BERLIN, Aug 30 (Reuters) - Borussia Dortmund have signed German youth international Jeremy Toljan on a five-year deal from Hoffenheim as they look to strengthen their backline, the Bundesliga club said on Wednesday. The 23-year-old, a recent under-21 European champion who also won a silver medal with Germany at the 2016 Olympic Games, made his league debut at Hoffenheim in 2013. "Jeremy can slot in on both the left and right of defence," Dortmund sports director Michael Zorc said in a statement. "He was one of the cornerstones of the side that secured the title for Germany at the U21 European Championship this summer. He is a player with great potential." Dortmund, who will compete in the Champions League this season, also extended the contract of 19-year-old defender Felix Passlack until 2021 but have sent him out on a two-year loan deal at Hoffenheim to gain more match practice. He will return in 2019. (Reporting by Karolos Grohmann; Editing by John O'Brien)