1. 1) W. Bao, Y. Qiu, Q. Huang, M.A. Green, P. Zajdel, M.R. Fitzsimmons, M. Zhernenkov, S. Chang, M. Fang, B. Qian, E.K. Vehstedt, J. Yang, H.M. Pham, L. Spinu and Z.Q. Mao : Phys. Rev. Lett. 102, 247001 (2009).
2. 2) A.M. Turner, F. Wang and A. Vishwanath : Phys. Rev. B 80, 224504 (2009).
3. 3) Y. Xia, D. Qian, L. Wray, D. Hsieh, G.F. Chen, J.L. Luo, N.L. Wang and M.Z. Hasan : Phys. Rev. Lett. 103, 037002 (2009).
4. 4) S. Jobic, P. Deniard, R. Brec, J. Rouxel, A. Jouanneaux and A.N. Fitch : Z. Anorg. Allg. Chem. 598, 199 (1991).
5. 5) D. Ootsuki, Y. Wakisaka, S. Pyon, K. Kudo, M. Nohara, M. Arita, H. Anzai, H. Namatame, M. Taniguchi, N.L. Saini and T. Mizokawa : Phys. Rev. B 86, 014519 (2012).