Aterian Plc announced a positive update of field activities being undertaken by Rio Tinto Mining and Exploration Ltd. on the lithium-focused Earn-In Investment and Joint Venture Agreement in the Republic of Rwanda. Aterian's local subsidiary, Kinunga Mining Limited, is engaged in supporting Rio Tinto in staging the necessary equipment to establish a maiden drill program over the licence area in 2024. A summary of activities being managed and operated by Rio Tinto is given below: Licence-wide geological surface mapping has been completed on road exposures throughout the licence, with an emphasis on capturing lithology and structural data.

Additional infill mapping has been completed over multiple targets within the licence, including HCK-1, HCK-2, the southeast area, and Buranga. Participation in local community projects, including donating and planting 3,000 tree saplings over the project. A reinterpretation of the Aterian geochemical soil samples collected from a 400 x 200m wide-spaced sampling campaign has identified several new anomalies (Li-Cs-Ta-Sn).

Follow-up closer-spaced sampling of isolated anomalies will be undertaken in 2024. Two soil orientation sampling lines were completed over HCK-1, with 74 samples collected at depths (from the surface) of 30cm, 50cm and 1m, collected over 27 sampling sites at 40m spacing. Results will inform the optimum sampling depth for further sampling campaigns in 2024.

A ground-based magnetic survey over the whole licence was completed in November at 100m line spacing, totaling 253 line-km. Initial orientation radiometric lines over HCK-1 have shown this to help identify covered (blind to surface) pegmatites. The trial has been extended to a 156 line-km survey west of the Mwogo River, with the eastern bank expected to be completed in early 2024.

Aterian has a Joint Venture and Operating Agreement with HCK Mining Company Limited, a private, non-related Rwandan registered entity over a 2,750-hectare exploration licence in southern Rwanda. Aterian holds a 70% interest in Kinunga Mining Limited, which holds the licence for the Project, with HCK Mining Company Limited having a 30% interest. The licence is located approximately 65 km southwest of Kigali and 20 km northwest of Huye, within the Southern Province, straddling the Nyanza and Huye District boundaries.

Rio Tinto has the option to invest US$7.5 million in two stages to earn up to a 75% interest in the HCK Licence to explore for minerals vital for a successful energy transition to renewable energy. Stage 1 exploration, currently underway, has commitment expenditures of US$3 million over a period of up to two years to earn a 51% interest in the Licence. Stage 2 exploration expenditures of US$4.5 million over a follow-on period of up to three years to earn a further 24% interest in the Licence, taking Rio Tinto's interest in the Licence to 75%.

A 2% capped Net smelter return ("NSR") granted over the Project (capped at US$50 million). Rio Tinto has the option to add Aterian's two other existing Rwandan projects, pending licence approval with the authorities.