William Buick (pictured) will partner Ivanhowe in the Prix de l'Arc de Triomphe at Longchamp on Sunday.
Trainer Jean-Pierre Carvalho and owners Gestut Schlenderhan had been considering their options for some time, and have now swooped for the star British rider.
Germany's big hope is a significant player in Europe's premier race after he defeated Sea The Moon by three lengths in the Group One Grosser Preis von Baden on September 7.
Carvalho said: "I'm very happy to get William Buick. He's a very good jockey. He's very strong. I know William and I know his father (Walter), who rode in Germany before. It was a very good decision.
"We had four or five jockeys in mind for the Arc and we had the choice of William Buick or Ryan Moore, but Ryan Moore, I think, may be riding for Aidan O'Brien."
Christophe Lemaire suffered an injury scare at Maisons-Laffitte on Monday but is not concerned about his fitness ahead of the big race on Sunday.
The French jockey sustained a slight leg injury in a fall at the Paris track but is not in action again until Friday and is looking forward to the big meeting at Longchamp on Saturday and Sunday.
"I'm fine. I'm just sore in the leg but it's not a problem," he said. "I have three days off without riding so I will be back on Friday."
Lemaire's book of rides includes Avenir Certain in the Arc itself, which he is yet to win. He picked up the mount on the dual French Classic winner after her regular pilot Gregory Benoist rejected her in favour of Ectot, who staked his claim with victory in the Prix Niel over the course and distance earlier this month.
Avenir Certain was among 20 horses to stand their ground at the first forfeit stage. The possibles are headed by ante-post favourite Taghrooda, winner of the Investec Oaks and King George VI And Queen Elizabeth Stakes.
Ectot is also there as is last year's heroine Treve, along with the Japanese trio of Gold Ship, Just A Way and Harp Star.
Aidan O'Brien has left in Chicquita and Ruler Of the World while St Leger victor Kingston Hill is Roger Varian's hope.