How can include space and german characters in laravel request rules?

Currently I am working on laravel 5.5 project. I need to validate a field. That field must be required, alpha numeric and space would be accept. I have added rules like 'street' => 'required|alpha_num|max:255'. But space not accept and german language not accepting eg:Betrag für diese. Any help would be appreciated.

via Chebli Mohamed