LONDON (Reuters) - British asset manager Schroders (SDR.L) expressed interest in buying CarVal Investors in May but the hedge fund that is owned by U.S. agri group Cargill said it was not for sale, a CarVal executive said. CarVal, with $11.6 billion under management placing it in the top 2 percent of global hedge funds, would have been a major acquisition for Schroders as it expands its product range. “Schroders ... said they would be interested in looking at ways we could work together,” CarVal Managing Principal Lucas Detor told Reuters.