High-pressure Raman study of the alkaline-earth metal fulleride, Ca2.75C60

The structural stability and electronic properties of [Formula: see text] are probed by means of high-pressure Raman spectroscopy using two different pressure transmitting media that lead to practically identical results. Although [Formula: see text] is isostructural with the rare-earth metal fulleride, [Formula: see text] of the same stoichiometry, the pressure coefficients of characteristic intramolecular [Formula: see text] modes are larger than those in the [Formula: see text] counterpart but similar to those in the pristine [Formula: see text] solid. Since the reduced pressure coefficients in the Sm fulleride have been attributed to strong [Formula: see text] coupling, our findings for the isostructural Ca fulleride are compatible with a reduced orbital mixing and [Formula: see text] coupling.