Magnetoresistance and thermoelectric power of La-chalcogenides (La2.989S4,La2.985Se4, Ce3S4)

The electrical transport properties of La-chalcogenides (La2.989S4, La2.985 Se4, Ce3S4) are investigated by measuring the magneto resistance and thermo electric power (TEP). The superconducting La2.989S4 with T-c = 8.2 K shows a clear phase transition at around T similar to 90 K, which is consistent w ith the structural phase transition temperature. La2.985Se4 is also superco nducting with T-c = 5.7 K. In the case of Ce3S4, the ferromagnetic transiti on is observed at T-m = 7.2 K and there is no superconducting or structural phase transition. The temperature dependence of TEP of the above three La- chalcogenides shows metallic characteristics with magnitudes of -10 muV/K a t room temperature, The broad peak at low temperature in TEP of Ce3S4 is di scussed with the role of the f-electron in Ce3S4 comparing with superconduc ting La2.989S4 and La2.985Se4. (C) 2001 Elsevier Science B.V. All rights re served.