Nottingham Forest have signed Ivory Coast defender Ousmane Diomande from Portuguese club Sporting for a reported £34 million. The centre-back has agreed a four-year contract with the Premier League side. Diomande, who made his senior breakthrough at Sporting, becomes Forest's latest addition ahead of the new season. The fee is understood to be one of the club's record outlays for a defender. Diomande will be expected to add strength to Forest's back line as the club prepares for another campaign in England's top flight. Sporting had been keen to keep the player, but the offer from Forest met their valuation. Diomande's arrival is part of Forest's ongoing recruitment drive, with the club looking to build on their previous season's performance. No further details of the transfer were disclosed, but the deal is believed to include performance-related add-ons.