  Temperature dependent electrical resistivity and thermopower measurements
were carried out on Gd1-xCaxBaCo2O5.53 with x varying between 0 and 0.25. Ca
subsitution leads to the incorporation of holes (Co4+) into the system that
leads to a reduction in resistivity and a stabilisation of the ferromagnetic
phase at low temperatures. The temperature dependence of resistivity and
thermopower are markedly different in the Ca doped sample, with a dramatic
reduction in the resistivity, as compared to that in the pristine sample. The
variation in both the resistivity and thermopower with temperature is explained
in terms of the transport of polarons in the ferromagnetic phase of Ca doped
system.
