Allkem Ltd and Livent said on Wednesday they would combine in an all-stock deal to create the world's third-largest producer of lithium, a key metal for electric vehicle batteries.

Toyota Tsusho Corp, the Japanese automaker's trading arm, holds 6.16% of Allkem's shares. Toyota did not immediately respond to a request for comment.

"Toyota is aware of the transaction... it is quite positive, their reaction to the deal," Allkem CEO Martin Pérez de Solay told Reuters.

"We are all looking forward jointly with them on a larger and deeper business relationship with the Toyota group," he added in an interview.

Shares in Allkem rallied as much as 13.6% when they opened on Thursday after news of the deal broke Wednesday after markets closed, sparking a rally in Australia-listed lithium stock.

Livent shares ended up 5.2% on the New York Stock Exchange.

(Reporting by Melanie Burton and Yuka Obayashi.)