We report on the Seebeck coefficient (S) of Ln1−xCaxBa2Cu2.9Ga0.1O6+z(Ln=Nd,Dy; 0≤x≤0.2) as a function of temperature. For Ln=Dy,Sat 300 K decreased by a factor of 20 asx(Ca) increased from 0 to 0.2. For all the samples, for a restricted range of temperature,Scould be described byS=S0−&agr;TwhereS0, characteristic of each sample, is related toTcbyTc=82.4−0.64S0and &agr; is a constant. ©1995 American Institute of Physics.