1. Dipartimento
di Fisica, Sapienza Università di Roma, 00185 Roma, Italy
2. Department
of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
3. Istituto Officina dei Materiali CNR, Basovizza 34149 Trieste, Italy
4. High
Field Magnet Laboratory (HFML − EMFL), Radboud University, NL-6525
ED Nijmegen, The Netherlands
5. Istituto per la Microelettronica e i Microsistemi CNR, 00133 Roma, Italy