Dons Look For Kev Fee
The 23-year-old Scotland international's contract ran out this summer and he agreed a deal with Cardiff last week.
Rules on compensation payments apply only if a player under 24 moves within the same country having risen through the youth ranks at a club.
Aberdeen believe that a move within the United Kingdom should qualify.
A Pittodrie spokesman told the Evening Express last week: "We plan to fight this all the way.
"We have invested heavily to bring Kevin on over a number of years and believe we should be compensated."
Picture from BBC Sport.
Picture from BBC Sport.