Affirma Capital closed a $145 million deal that gives it a direct stake in a key supplier of power to some of the biggest Zambian and Congolese mines for copper and cobalt, metals that are pivotal to the transition to cleaner energy.

Affirma, formerly Standard Chartered Plc’s private equity arm, now directly holds 34.6% of Copperbelt Energy Corp., it said in a statement Monday. The company teamed up with Norway’s state-owned Norfund and Kommunal Landspensjonskasse Gjensidig Forsikringsselskap to fund the deal, it said.

Private equity firms usually exit companies after a set number of years to reward investors in their funds. Affirma decided to re-invest in Copperbelt Energy, with the initial funds having made a return of about three times their initial $74 million investment in the company in 2014, including dividends.

It’s the biggest yet so-called single-asset continuation deal in Africa, Affirma said.

Congo has rapidly caught up with Peru as the world’s second-biggest copper producer and is also the main source of cobalt. Both metals are critical for the transition away from fossil fuels to cleaner energies like electric vehicles.

Zambia also has ambitions to significantly grow its own copper output, with demand expected to outpace supply in the coming years.