Transport properties and CDW instabilities of the quasi-two-dimensional monophosphate tungsten bronzes (PO2)4(WO3)2m(m = 5)

Resistivity and magnetoresistance have been measured on single crystals of the monophosphate tungsten bronzes (PO 1 ) 4 (WO 3 ) 2m for m=5. The m = 5 compound exists in two structural varieties which lead to different resistivity and magnetoresistance properties. Shubnikov de Haas oscillations with large amplitude are observed in one of the variety. The origin of the observed anomalies in the resistivity vs temperature curves is discussed.