(CNN) Matthijs de Ligt, the 19-year-old Ajax captain who led the Dutch side to the Champions League semifinals, has completed his move to Juventus for a fee of $84.3 million.

A product of Ajax's famed youth academy , De Ligt becomes the fourth most expensive signing of the summer transfer window so far.

According to a statement from Juventus, the transfer fee is payable over five years with potential additional costs of $11.2 million.

De Ligt became Ajax's youngest captain four months before his 19th birthday, and last season helped the club to a league and cup double, as well as scoring against Juventus to reach the Champions League final four.

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