U.K.-based asset manager Baillie Gifford & Co., Tesla Inc.'s largest outside investor, has bought 85,297,388 common shares of Chinese electric-car maker Nio Inc.

Baillie Gifford, which owns 7.72% of Tesla's stock, now holds a greater stake of 11.44% in Nio, according to an Oct. 9 SEC filing.

Following the disclosure, Nio's recently floated stock jumped 22.35% to close at $7.39 on Oct. 9, valuing Baillie Gifford's investment at about $630.4 million.