1. Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
2. Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, North Haugh, University of St. Andrews, St. Andrews KY16 9SS, UK.
3. SUPA, School of Physics and Astronomy and Centre for Science at Extreme Conditions, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, UK.
4. Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
5. High Field Magnet Laboratory, Radboud University Nijmegen, Toernooiveld 7, 6525 ED Nijmegen, Netherlands.
6. Laboratory of Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA.
7. Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.