SOFIA: Serie A club Fiorentina have signed Bulgaria under-19 international defender Petko Hristov from Slavia Sofia on a five-year deal, both clubs said on Monday. The 18-year-old, considered to be one of the best young players in the Balkan country, was a key figure in Bulgaria's team at the European U-19 championship in Georgia this month. 'I'm ready for this challenge,' Hristov, who was a regular at the seven-times Bulgarian champions Slavia last season, making 30 appearances, said of his move to Italy. 'I'm such a type of footballer who never surrenders.' Fiorentina finished eighth in Serie A last season on 60 points from 38 matches.