IndyCar podium finisher Simona de Silvestro and ex-Formula 1 driver Sakon Yamamoto will join the Formula E field for its London finale on June 27-28.
De Silvestro, who recently drove the FE car in a demonstration run in Geneva, takes the second Andretti Autosport seat alongside Jean-Eric Vergne.
The sometime Sauber F1 development driver will become Andretti's eighth FE racer of the inaugural series, following Franck Montagny, Vergne, Charles Pic, Matthew Brabham, Marco Andretti, Scott Speed and the #28 car's last occupant Justin Wilson.
Yamamoto makes his racing comeback with Amlin Aguri, whose regular driver Antonio Felix da Costa has a clash with the Norisring DTM round.
Japanese 32-year-old Yamamoto contested 21 grands prix with Super Aguri, Spyker and HRT, split between the 2006, '07 and '10 seasons, but has not competed regularly since, although he did have a reserve role for the Virgin team in '11.
His best F1 result was 12th in his home grand prix at Fuji with Spyker in 2007.