According to the documentation of the Team creation in graph ( https://docs.microsoft.com/fr-fr/graph/api/team-put-teams?view=graph-rest-1.0&tabs=java), the type of expected HTTP request is a PUT (PUT /groups/{id}/team)
Thus, an example is given at the bottom of the page:
graphClient.groups("{id}").team().buildRequest().put(team);
However, the PUT method does not exist in the interface ITeamRequest.