Physical properties of ß″-(BEDT-TTF)₂ICl₂

A single crystal of ß″-(BEDT-TTF)₂ICl₂ was synthesized electrochemically, and the crystal structure was determined by X-ray analysis. This ß″-type crystal was characterized by means of the electrical resistivity, electron spin resonance, X-ray diffraction, and polarized reflectance spectrum. The temperature dependence of the electrical resistivity which was proportional to T down to 10 K shows a typical metallic behavior. The ESR spectrum exhibited a Dysonian line-shape. The intensity of the spin susceptibility abruptly decreased at 17 K, although the electrical resistivity and the Bragg diffraction intensity showed no discontinuous change: this indicates the occurrence of a magnetic phase transition. The reflectance spectrum for the //c polarization showed a Drude-like dispersion already at room temperature. The anisotropic two-dimensional electronic structure was examined by the reflectance spectrum analysis.