Manchester United on Wednesday completed the signing of Argentina defender Lisandro Martinez from Ajax for a fee that could reach nearly £57 million.
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.
"I've been lucky enough to be part of successful teams in my career and that's what I want to continue at Manchester United.
"There will be a lot of work to get to that moment, but I firmly believe that, under this manager and coaches, and together with my new team-mates, we can do it."
John Murtough, Manchester United football director, said: "Lisandro is an outstanding player who will bring further quality and experience to Erik (Ten Hag)'s squad."
Ajax said they had agreed a transfer fee of 57.37 million euros ($58.2 million, £48.3 million) with United. Including variables, that amount could increase to 67.37 million euros.