HERZOGENAURACH, Germany — Adidas AG and pop star Beyoncé joined forces to develop footwear and apparel, as the German sportswear company seeks to reignite growth in its casual fashion lineup.Beyonce, known for hits such as “Single Ladies,” last year ended a venture with U.K. fashion tycoon Philip Green, with the singer buying out his stake in her Ivy Park brand. Adidas said the new deal “respects Beyoncé's ownership of her company.”Adidas is adding Beyoncé to a roster of celebrity partners that already includes rapper Kanye West as it wrestles with a slowdown in demand for retro footwear like the Stan Smith and Superstar, which drove its growth for years. Archrival Nike Inc. has been gaining ground on the German company on its European home turf.Adidas shares rose as much as 1 percent after the announcement Thursday.Adidas Chief Executive Officer Kasper Rorsted has said he’s aiming to distribute West’s Yeezy line more widely this year in an effort to spur sales of fashion-related items. Shoes from the line can fetch $300, compared with $80 for a pair of Stan Smiths, and often resell for more than $1,000 to sneaker fans online.The company also has partnerships with musician Pharrell Williams and supermodel Karlie Kloss. Kylie Jenner, the cosmetics billionaire member of the Kardashian clan, joined the Adidas squad as a brand ambassador late last year, debuting in an ad campaign for a new running shoe in August.New ProductsAdidas said the partnership with Beyoncé will develop new products, including performance and lifestyle offerings. They will also focus on “empowering and enabling the next generation of athletes, creators and leaders,” the company said in a statement.Beyoncé started Ivy Park in 2016 with Green’s Topshop as an activewear line to be worn both in the gym and as casual street clothes. Products included black jerseys, sleeveless hoodies and mesh bomber jackets.She first got into fashion in 2004 with a label called House of Dereon. That brand fizzled over the years, unable to attract enough shoppers. Its kids’ line folded in 2012.By Eric Pfanner and Kim Bhasin, with assistance from Robert Williams.