Manchester United on Wednesday completed the signing of Argentina defender Lisandro Martinez from Ajax for a fee that could reach nearly 57 million pounds. The 24-year-old, who won two Eredivisie titles under new United boss Erik ten Hag in Amsterdam, has signed a contract until 2027 at Old Trafford, with the option of a further 12 months. "It's an honour to join this great football club," the centre-back told United's website. "I've worked so hard to get to this moment and, now that I'm here, I'm going to push myself even further.