User newAdminUser = await graphClient.Users.Request().AddAsync(new User
{
    AccountEnabled = true,
    DisplayName = userBinding.FullName,
    MailNickname = userBinding.UserName,
    UserPrincipalName = userBinding.UserName + '@' + domain,
    PasswordProfile = new PasswordProfile
    {
        Password = new NetworkCredential(string.Empty, minervaUser.Password).Password,
        ForceChangePasswordNextSignIn = true
    }
});

await graphClient.Users[newAdminUser.Id].Request().UpdateAsync(new User()
{
    UserType = "Global Administrator"
});