These results confirm diffuson-mediated thermal transport in the Ag + argyrodites at temperatures relevant for thermoelectrics and ionic conduction. Accordingly, the phonon-gas channel has only a minor contribution. It can be concluded that a complex crystal structure, resulting in many energetically close phonon modes, and relatively large anharmonicities are sufficient to achieve diffuson-dominated thermal transport in crystalline materials. This is to say that we do not need to explicitly invoke ion transport effects in order to capture the magnitude of thermal conductivity. Thus, significant diffuson-contributions can be expected in other structurally well-defined materials.