Anomalous electrical and magnetic behavior in (PO2)4(WO3)2m (m=4)

Single crystals of P4W8O32 {(PO2)4(WO3)2m, m=4} were prepared by chemical-vapor transport technique with KI as the transport agent. The temperature dependence of electrical resistivity in the range 2300 K shows metallic behavior with two anomalies at 60 and 85 K. The room-temperature resistivities along the long- and short-plate axis of a single crystal (a and b axes) are 3×10-4 and 2×10-4 cm while that perpendicular to the crystal plate (c axis) is 7×10-3 cm. The relatively higher conductivities in the crystallographic a-b plane confirm that the compound is a quasi-two-dimensional metal. Seebeck measurement indicates that at room temperature the primary charge carriers are electrons. The magnetic susceptibility is temperature independent down to 92 K. At 92 and 56 K sharp decreases in the susceptibility are observed. The anomalous behavior in the magnetic susceptibility and electrical resistivity of P4W8O32 at low temperatures is indicative of the onset of charge-density-wave states and is consistent with the proposed band electronic structure.