15 April 2026

Aterian plc

("Aterian" or the "Company" or the "Group")

Ground Magnetics Underway at Agdz Cu-Ag Project

Aterian plc (AIM: ATN), the Africa-focused critical metals exploration company, is pleased to announce the commencement of a ground-based magnetic geophysical survey at its 100%-owned Agdz Copper-Silver Project ("Agdz" or the "Project") in the Kingdom of Morocco ("Morocco").

The programme represents a key step in advancing Agdz from surface discovery towards drill target definition, following the Company's recent announcement on 29 January 2026, which highlighted a significant expansion in the footprint of copper-silver mineralisation.

Highlights:

·      111 line km ground magnetic survey underway across 11.20 km².

·      c.28% of the planned survey completed.

·      Survey targeting fault-controlled copper-silver bearing breccias identified in recent fieldwork.

·      Mineralisation traced over up to 0.9 km strike, with potential for further extension.

·      Following up on historic and recent assays, including 3.47 % Cu with 136 g/t Ag and 1.34 % Cu with 31 g/t Ag.

·      Expanding total ground magnetic coverage to 322 line km over 20.8 km² (from 195 line km historically)

·      This objective is to rapidly define new drill-ready targets across an expanding mineralised footprint.

Strategic Context

The current programme is designed to define the geometry, continuity and scale potential of multiple sub-parallel, structurally controlled mineralised zones, while also exploring for new unrecognised targets across underexplored areas of the Project.

The survey forms part of a systematic exploration workflow that integrates geophysics with ongoing field mapping and sampling, with the objective of rapidly generating a pipeline of high-quality, drill-ready targets.

Importantly, the results of the ground magnetics programme will be integrated with the structural targeting work currently being undertaken by Lithosquare, enabling a multi-disciplinary approach to target refinement and prioritisation.

Charles Bray, Chairman of Aterian, commented:

"The launch of this ground magnetics programme marks the next step forward in progressing Agdz from surface discovery towards new drill target definition.

Following the encouraging results announced earlier this year, which expanded the mineralised footprint and the prior exploratory drilling results, we are now systematically advancing our understanding of the scale and continuity of the system, both along strike and across previously underexplored areas. The results from this survey will also directly support and enhance Lithosquare's targeting work, ensuring that multiple datasets are integrated to refine and prioritise high-quality targets.

With the survey progressing well and supported by parallel fieldwork, we are focused on rapidly refining targets and building a robust pipeline of drill-ready opportunities as we move Agdz into its next phase of exploration."

Ground Magnetics Programme

The survey is designed to define the along-strike continuity of multiple sub-parallel, linear copper-bearing fault breccias, which individually outcrop discontinuously over a strike length of up to 0.9 km. The programme also targets the identification of additional prospective structures that may be hidden beneath the surface.

The programme is being conducted by an independent geophysical contractor using a GEM GSM-19 Overhauser magnetometer, with the following parameters:

·      60 lines for a total of 111 line km.

·      Average line length - 1.85 km.

·      100 m line spacing.

·      Three contiguous grids covering a total of 11.20 km².

·      Estimated a two-week timeframe for data acquisition.

·      Modelling, interpretation and reporting are estimated at 4 weeks.

Next Steps

Based on the results of the ground magnetics survey, the Company intends to:

·      Define priority target areas for follow-up work.

·      Undertake detailed geological mapping and trenching.

·      Undertake an Induced Polarisation (IP) / resistivity survey over priority targets.

·      Advance a ranked pipeline of drill-ready targets.

Project Summary

Aterian holds a 100% interest in the 50.4 km² Agdz Copper-Silver Project, comprising the 34.5 km² Agdz licence and the adjacent 15.9 km² Agdz Est licence in central Morocco.

The Project is located in the highly prospective Anti-Atlas Mountains within the Drâa Tafilalet region, approximately 35 km east of Ouarzazate, a well-serviced regional hub with an airport and established infrastructure. The Project benefits from excellent access via paved and unpaved roads. It is situated approximately 40 km southeast of the Noor solar power complex, one of the world's largest renewable energy facilities.

Agdz is located within Morocco's highly prospective Anti-Atlas belt, a stable and well-established mining jurisdiction with growing strategic importance for copper supply.

The Agdz Project is situated within a well-established copper-silver mining district, approximately 14 km southwest of the Bouskour copper-silver mine (19 Mt at 1.44 % Cu and 12 g/t Ag Measured & Indicated and 9 Mt at 1.61 % Cu Proven & Probable​¹​​​) and within trucking distance of existing mining infrastructure. The world-class Imiter silver mine (192 M Oz Ag Measured & Indicated and 152 M Oz Ag Proven & Probable²) lies approximately 80 km northeast of the Project, with both operations owned by Managem Group. While mineralisation at neighbouring deposits is not necessarily indicative of mineralisation at Agdz, their presence underscores the district-scale prospectivity of the Anti-Atlas Belt.

Illustrations
The following figures/images have been prepared by Aterian and relate to the disclosures in this announcement.

Qualified Person

The technical disclosure in this regulatory announcement has been approved by Simon Rollason, Chief Executive Officer of Aterian Plc. A graduate of the University of the Witwatersrand in Geology (Hons). He is a Member of the Institute of Materials, Minerals and Mining, with over 30 years of experience in mineral exploration and mining.

- ENDS -

This announcement contains information which, prior to its disclosure, was inside information as stipulated under Regulation 11 of the Market Abuse (Amendment) (EU Exit) Regulations 2019/310 (as amended).

Engage directly with the Aterian PLC management team by asking questions, watching video summaries, and seeing what other shareholders have to say. Please navigate to our interactive investor hub here: https://aterianplc.com/s/fcf8eb

For further information, please visit the Company's website: www.aterianplc.com or contact:

Aterian Plc:

Charles Bray, Executive Chairman - [email protected]

Simon Rollason, CEO & Director - [email protected]

Financial Adviser and Joint Broker:

AlbR Capital Limited

David Coffman / Dan Harris

Tel: +44 (0)207 7469 0930

Joint Broker:

SP Angel Corporate Finance LLP

Ewan Leggat / Devik Mehta 

Tel: +44 20 3470 0470

Financial PR:

Bald Voodoo - [email protected]

Ben Kilbey
Tel: +44 (0)7811 209 344

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Notes to Editors:

About Aterian plc

www.aterianplc.com

Aterian plc is an LSE-listed exploration and development company with a diversified African portfolio of critical metals projects.

Aterian plc is actively seeking to acquire and develop new critical metal resources to strengthen its existing asset base while supporting ethical and sustainable supply chains as the world transitions to a sustainable, renewable future. The supply of these metals is vital for developing the renewable energy, automotive, and electronic manufacturing sectors, which are increasingly important in reducing carbon emissions and meeting global climate ambitions.

Aterian has a portfolio of multiple copper-silver (+gold) and base-metal projects in Morocco. Aterian holds a 90% interest in Atlantis Metals, a private Botswana-registered company holding eleven mineral prospecting licences for copper-silver in the world-renowned Kalahari Copperbelt and three for lithium and salt brine exploration in the Makgadikgadi Pans region. The Company also holds an exploration licence in southern Rwanda, where it is evaluating the tantalum and niobium opportunity, in addition to further exploring for pegmatite-hosted lithium.

The Company's strategy is to seek new exploration and production opportunities across the African continent and to develop new sources of critical mineral assets for exploration, development, and trading.

Glossary of Terms

The following is a glossary of technical terms: