The electrical resistivity rho(T,x) and magnetic susceptibility chi(T,
H), and specific heat C(T,x) have been measured on single crystals of
Y-1-x TbxBa2Cu3O7. The results strongly suggest the appearance of stro
ng 4f electron hybridization. It becomes apparent that the Tb doped sy
stem possesses properties that largely deviate from the well-known beh
avior of the other high T-c and doped high T-c systems.