1. Eduard Zintl Institute of Inorganic and Physical Chemistry, Technische Universität Darmstadt, Alarich-Weiss-Straße 12, 64287 Darmstadt, Germany
2. School of Molecular Sciences, Arizona State University, Tempe, Arizona 85282, United States
3. Faculty of Physics and Center for Nanointegration Duisburg-Essen, University of Duisburg-Essen, 47057 Duisburg, Germany
4. Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
5. Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany