Thermoelectric power of the thallium-based superconductor ${\mathrm{Tl}}_2$${\mathrm{Ba}}_2$${\mathrm{Ca}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{10\mathrm{-}\mathrm{\delta }}$

The temperature dependence of the thermoelectric power of the high-temperature superconductor ${\mathrm{Tl}}_2$ ${\mathrm{Ba}}_2$ ${\mathrm{Ca}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{10\mathrm{-}\mathrm{\delta }}$ is reported. The contribution of holes from the valence band satisfying a Fermi-liquid model gives the major part of the measured thermoelectric power. The results show that the conduction-band electrons also contribute to the total output of the thermoelectric power and the portion of the electron’s contribution increases with temperature. An explicit expression for the thermolectric power of the 2:2:2:3 phase was derived based on a two-band model and the experimental data, which is given as S(μV)=0.121T-(280-0.2T)${\mathit{e}}^{\mathrm{-}550/\mathit{T}}$. A general formula, S=AT+(Bλ+CT)exp(-λ/T), is found to give a close description of the thermoelectric power of various cuprate high-${\mathit{T}}_{\mathit{c}}$ superconductors.