The winger was signed earlier this summer from Sporting CP.
He said at his presentation: "I am very happy to be able to return home. It has always been a dream, since I was a child, also for my family and friends.
"Being here is the biggest present I could give them and I am very happy about it."
Djalo added: "I come with a great desire to learn every day and I think I'm at the best moment of my career. We will face the challenges seriously and with a lot of hard work. That's how things will work out on the pitch, in a natural way."
Fellow addition Andoni Gorosabel, from Alaves, also said yesterday's presentation: "I come to a great club, that attracts and that won the Cup and is going to play in Europe, I have taken everything into account. I'm very happy to be here. I'm here to bring enthusiasm, commitment and competitiveness in a very nice and difficult year, with four competitions. We will go for everything."