Rb 3 Er 4 Cu 5 Te 10 : Exploring the Frontier between Polar Intermetallics and Zintl‐Phases via Experimental and Quantumchemical Approaches

The tailored design of solid‐state materials requires a proper understanding of their respective electronic structures. In order to rationalize the relationships between crystal structures and electronic structures in intermetallic compounds, the Zintl‐Klemm concept has been frequently employed. Yet, the frontier between the valence‐electron concentrations ( e / a ) of the Zintl‐ and the polar intermetallic phases has remained unclear to date. To shed some light on this frontier, we explored the electronic structure of the quaternary compound Rb 3 Er 4 Cu 5 Te 10 . To this effect, the crystal structure of this telluride, which was obtained as pure phase from high‐temperature reactions, was determined by means of X‐ray diffraction experiments for the very first time. In addition, the magnetic properties of the Rb 3 Er 4 Cu 5 Te 10 were also determined in order to explore the erbium 4 f states in more detail.