DAKAR, Jan 27 (Reuters) - The Democratic Republic of Congo and its Chinese investors have reached an agreement over their Sicomines copper and cobalt joint venture, they said in a statement on Saturday, with the Chinese investing up to $7 billion in infrastructure projects.

Both parties agreed to maintain the current structure of the shareholding, while the Chinese partners, including Sinohydro and China Railway group, will pay 1.2% of royalties annually to Congo, the statement said.

Congo is the world's biggest producer of cobalt, a key component in batteries for electric cars and mobile phones. It is also the world's third-largest copper producer and holds significant deposits of lithium, tin, tungsten, tantalum and gold.

The Congolese mining sector, particularly its copper and cobalt mines, is now largely dominated by Chinese companies. (Reporting by Sonia Rolley, Writing by Portia Crowe, Editing by William Maclean and Nick Macfie)