LOW-TEMPERATURE CRYSTAL AND BAND ELECTRONIC-STRUCTURES OF METALLIC M(DMIT)(2)(M=NI, PD) COMPOUND

The crystal structure of alpha[(CH3)(2)(C2H5)(2)N][Ni(dmit)(2)](2)(dmit=1,3-dithiol-2-thione-4,5-dithiolate) was determined at 11 K by use of newly developed X-ray system based on the imaging plate(IP) equipped with closed cycle He refrigerator. The space group of C2/c of the high-temperature phase changes to P21/c at low temperature. The extended Huckel tight-binding band calculation based on the 11K structure and the X-ray evidence showing the appearance of the twofold superlattice gave two-dimensional Fermi surfaces, which are consistent with those derived from the experiments on the magnetoresistance oscillation.