ESR study on α-(BEDT-TTF)2KHg(SCN)4 single crystal

X-band ESR measurements have been carried out on a α-(BEDT-TTF)2KHg(SCN)4 single crystal at temperatures between 1.5 and 30 K. The principal axis and values of g-tensor are determined. The directions of g1 = 2.0014, g2 = 2.0029 and g3 = 2.0128 are near the directions of the c-, a- and b-axis, respectively. Angular dependence of the effective g-value in the g1g2-plane is much smaller than that in the g1g3- and g2g3-planes. The splitting of resonance line appears below 4.2 K. While the line width of one split line increases with decreasing temperature down to 1.5 K, that of another one is almost independent of temperature. The splitting seems to be related to the SDW state, which is suggested to exist below 8 K.