1. Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, via Roberto Cozzi 55, I-20125 Milano, Italy
2. Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
3. Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
4. National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
5. Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia