Does anyone know if it's possible for TK to link an Alaska Airlines (Star Alliance) PNR to a TK PNR? TK customer service says it's impossible but I can find the Amadeus commands to do it.

I am flying KIV-IST-SFO on TK and then SFO-PHX on Alaska and would like to be able to interline my baggage at check-in in KIV. I would have bought the whole ticket with TK but they couldn't see any availability for the last leg in their system. If it makes any difference all flights are business. Thanks for your help.