"The main reason I've decided to come is the feeling this club gives me. After a game against Real Madrid I got the feeling this was a very big club," he said.
"I'm hugely motivated."
Adan, who will be officially presented by Betis on Wednesday, added of his new club's league predicament: "I'm aware of the situation that the club is in but I had to take this step.
"The important thing is to be realistic. The situation is difficult but the first thing is to give everything on the pitch."
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