[1] RAS, PL Kapitza Inst Phys Problems, Moscow 119334, Russia
[2] Univ Augsburg, Ctr Elect Correlat & Magnetism EKM, Expt Phys 5, D-86135 Augsburg, Germany
[3] Natl High Magnet Field Lab, Tallahassee, FL 32310 USA
[4] Tech Univ Wien, Inst Festkorperphys, A-1040 Vienna, Austria
[5] Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England