HALL-EFFECT IN THE ORGANIC CONDUCTOR ALPHA-(BEDT-TTF)2KHG(SCN)4, WHERE BEDT-TTF IS BIS(ETHYLENEDITHIO)TETRATHIAFULVALENE

Hall-effect measurements below 20 K and up to 23 T on single crystals of the organic conductor alpha(BEDT-TTF)2KHg(SCN)4 are reported. The sign of the Hall coefficient R(H) is positive in the whole temperature range, indicating a hole carrier. R(H) obtained from the H-linear dependence of the Hall resistance R(xy) steeply increases below 10 K and saturates around 4 K. This increase in R(H) coincides with anomalies observed in the static magnetic susceptibility and the electrical resistance at about 10 K. This finding suggests a reconstruction of the Fermi surface associated with the spin-density-wave (SDW) gap formation in this magnetic-phase transition. The high-field R(xy) above about 10 T at 4.2 K deviates from the H-linear dependence, suggesting that the SDW formation might change with fields.