Unix (pam) authorization with required public key

Hello!

I want to set ssh authorization through unix/pam with mandatory public
key. I want will make sure that except the password the user has an
acknowledgement of legitimacy in the form of a public key. Thus the
password should be from unix/pam, not from key.

I tried different variants. It turned out with key and without the
password, or the password undertook from a key, instead of from
unix/pam.

Whether such variant is possible?

OpenSSH_4.7p1 Debian-8ubuntu1.2, OpenSSL 0.9.8g 19 Oct 2007

-- 
Yours faithfully, Ilya Skorik