Soccer-Argentine Di Santo joins Schalke from Werder

(Adds Schalke confirmation) BERLIN, July 25 (Reuters) - Argentine striker Franco Di Santo has made use of a buy-out clause in his contract with Werder Bremen to leave the north German club and join Bundesliga rivals Schalke 04. The 26-year-old has signed a four-year contract with Schalke, his new club said on their website (www.schalke04.de) on Saturday. The powerful former Chelsea forward, who has scored 17 goals in 49 Bundesliga matches, joined Werder from English club Wigan Athletic in 2013. Di Santo was a key figure in Werder's strong league finish last season when they climbed out of the relegation zone after the winter break and narrowly missed out on a Europa League spot. (Reporting by Karolos Grohmann, editing by Tony Jimenez)