LONDON (Reuters) - Formula One champions and former Mercedes team mates Nico Rosberg and Lewis Hamilton are set to lock horns again as owners of rival outfits in the new Extreme E electric off-road series starting next year.

Rosberg, who retired from Formula One after beating Hamilton to the 2016 title, announced on Thursday that his Rosberg Xtreme Racing (RXR) had become the ninth team confirmed for the inaugural season.