1. Department of Physics and Astronomy, University of Utah, 115 S, 1400 E, Salt Lake City, Utah 84112, United States
2. National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
3. Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstrasse 31, 93040 Regensburg, Germany