Hi @ChenBr,
Unfortunately there is no way to enforce biometric fingerprint or face recognition sign-in and deny PIN or any other similar unlocking method. It will only ask the user for the information required to unlock the screen, whichever one the user chooses.
As stated in the docs the device biometrics lets you choose between providing what you are (fingerprint or FaceID) and what you know (PIN or Pattern).
Have a good one,
Vlad