The structure of Sm_2.75C₆₀ is determined using the Rietveld method; it is found that Sm_2.75C₆₀ is isostructural with Yb_2.75C₆₀. Raman spectra are displayed, and there is an anomalously broad distribution of vibrational structures for the low-frequency H_g modes and around the A_g(2) mode, which can be related to the complexity of the Sm_2.75C₆₀ structure. The H_g(2) mode is split into five components, allowing a quantitative analysis based on the electron-phonon coupling theory.