The 23-year-old former Newcastle striker headed for the Stadium of Light via Cardiff in a deal which could eventually amount to £5million with the furore over the switch rumbling on.
And Black Cats manager Roy Keane said: "I am delighted that Michael has joined us. He is a natural goalscorer who will bring competition with our other quality strikers to the side. I am very confident he will score goals for this football club."
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