1. Institute for Solid State Physics, University of Tokyo, Minato-ku, Tokyo 106
2. College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156
3. Department of Physics, Aoyama-Gakuin University, Setagaya-ku, Tokyo 157
4. NTT Basic Research Laboratories, Atsugi-shi, Kanagawa 243-01
5. Department of Superconductivity, University of Tokyo, Bunkyo-ku, Tokyo 113