1. Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
2. Department of Physics and Astronomy and Center for Condensed Matter Theory, Rutgers University, Piscataway, NJ 08854–8019, USA.
3. Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831–6475, USA.
4. European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe, Germany.