TRANSPORT-PROPERTIES OF ORGANIC METAL-CONTAINING MAGNETIC IONS (BEDT-TTF)(2)CSCO(SCN)(4)

In order to investigate the nature oi the 20 K metal-to-insulator tran sition of the title organic metal, (BEDT-TTF)(2)Cs Co(SCN)(4) (BEDT-TT F: bis(ethylenedithio) tetrathiafulvalene), which involves localized s pins on Co2+ in the anion layers in addition to the itinerant electron s on the donor molecules, measurements of electrical resistivity under pressure, magnetoresistance, and thermoelectric power have been carri ed out. The pressure raises the metal-to-insulator transition temperat ure, but the transition is not affected by the magnetic field. The the rmoelectric power does not show any clear anomaly near the transition. These observations suggest that the origin of the metal-to-insulator transition is related neither to the magnetic order of the localized s pins on Co2+ nor to simple SDW or CDW, but preferably related to the c orrelation of the donor electrons.