The 24-year-old, who scored 17 goals last season, has become Lyon's first signing since winning their third consecutive Ligue 1 title. "An agreement has been reached between player and directors of both clubs," read a Sochaux statement.
A former French Under-21 international, he has been called up to the senior national team a number of times but is yet to make his debut. Sochaux had been Frau's only club before he agreed to sign for Lyon. He won the French League Cup with Sochaux this season and helped earn a fifth-placed finish in Ligue 1 and a place in the UEFA Cup.
With his former Sochaux team-mate Benoît Pedretti having joined Olympique de Marseille, Frau is the second major player from the side from the east of France to leave the club this summer. However, with both expected to command a sizeable transfer fee, the Sochaux academy will receive plenty of encouragement in its aim to discover new talent.
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