The Catalans lowered their asking price of €8m to €5m to offload the Spaniard whose contract at Camp Nou expires in 2022.
Alena already joined Getafe in the mid-season of 2020/21 on loan, and has been a target for coach Michel to make the deal permanent.
The new deal will see Barcelona pocketing 50 percent of any future sale of the 23-year-old, also a buy-back clause and first option to buy the player anytime he's available for sale, are equally included in the deal.