1. Institute of Physics, Wrocław University of Technology, 50-370 Wroclaw, Poland
2. Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA, Grenoble, France
3. Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany
4. Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
5. Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 OHE, United Kingdom