Thermoelectric power of Tl/sub 2/Ba/sub 2/(Ca/sub 1-chi/Mg/sub chi/)/sub 2/Cu/sub 3/O/sub y/ superconductors

Thermopower of a series of Tl/sub 2/Ba/sub 2/(Ca/sub 1-x/Mg/sub x/)/sub 2/Cu/sub 3/O/sub y/ superconductors has been measured in a temperature range of 77-300 {Kappa}. The data are analyzed on the assumption that there are two regions in the samples: metallic and semiconductive. It is found that the diffusion thermopower of the metallic region, which is the normal state of the superconductive phase in the sample, is proportional to the temperature and has a small as well as negative value.