The team contains a person that does the social and interpersonal things necessary to keep the team unified
Make sure that the team contains a ‘Matron’ who will do the social and interpersonal things necessary to keep the team unified. The things needed to keep a team unified will vary with culture, but this involves noting events that should be celebrated (birthdays, milestones?) and arranging suitable celebrations (cakes? Beer and curry?).
Teams need to play together sometime. There may be few celebratory activities that all would enjoy, so don’t always choose the same approach that excludes the same people. The Matron role is something people do naturally, they cannot be given it to do as a task. Find a natural ‘Matron’ and include them in the team.