A unit of billionaire Carlos Slim’s Grupo Carso is purchasing a 49.9% minority stake in Talos Energy’s Mexico unit for $125 million.

The deal will give Carso access to Talos’ 17.4% stake in the Zama mega oil field, with the price implying a minimum valuation of about $250 million for Talos’ stake in the field. Talos will keep control of the remaining 50.1% of its local unit, Talos Mexico, the company said. The transaction is pending approval from the local regulator.

Talos previously had sparred with Petroleos Mexicanos over the development of Zama after Mexican authorities said Pemex would operate it following the discovery that it bled into a reservoir owned by the Mexican state oil behemoth. The companies finalized in March a plan to develop the field in partnership.

The divestment by Talos comes at a time that companies are facing increasing uncertainty after a series of business-unfriendly moves by Mexican President Andres Manuel Lopez Obrador, including the expropriation of a rail line.

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Slim also has exploration, oil drilling and services operations through Carso Energy in Mexico and Colombia, and exploration contracts in Mexico. The company also operates several natural gas pipelines in northern Mexico and Texas.

--With assistance from Andrea Navarro.