Comment on `Electronic Properties of Red P-Type Tl2S5 Single Crystals'

Recently, Gamal et al. Chin. Phys. Lett. 22 (2005) 1530] reported the results of electrical conductivity, Hall effect and thermoelectric measurements on p-type Tl2S5 single crystals. From the experimental data for the temperature dependence of differential thermoelectric power, Gamal et al. determined thevalues of 2.66×10-41kg and 2.50×10-41kg, respectively, for the effective masses of electrons and holes in p-type Tl2S5, which are about ten orders of magnitude smaller than the free electron mass (9.11×10-31kg). We argue that the anomalously small values obtained for the effective mass of chargecarriers in Tl2S5 have no physical significance.