The Hall coefficient RH has been measured in ceramic samples of the high-Tc superconductors Bi-Ca-Sr-Cu-O and Tl2Ca2Ba2Cu3Ox. The Bi compound is a mixture of the 2:1:2:2 and 2:2:2:3 phases whereas the Tl compound is single-phase 2:2:2:3. In both systems, RH is T dependent and positive. A 1T dependence is observed in the Bi compound. We discuss the significance of the low Hall number 1RHe (equivalent to 0.1 holes per Cu ion near Tc) implied by the large RH observed in both systems.
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