1. University of Bremen, Institute of Inorganic Chemistry and Crystallography, Leobener Straße 7, D-28359 Bremen, Germany
2. University of Bremen, MAPEX center for materials and processes, Bibliothekstraße 1, D-28359 Bremen Germany
3. Institute for Condensed Matter Physics, Technische Universität Braunschweig, Mendelssohnstraße 3, D-38106 Braunschweig, Germany