The phonon gas channel contributions, !" , dominate the total lattice thermal conductivity at low-temperatures and well-describe the peak in thermal conductivity (Figure ). With increasing temperature, the phonon gas channel declines while vice-versa the diffuson contributions, $ %% , increase strongly, before plateauing above 100 K. The resulting total lattice thermal conductivity of the two-channel model, = !" + $ %% , captures both the magnitude and temperature-dependence of the experimental data, not only in the phonon (T < 50 K) and diffuson (T > 100 K) mediated regimes but also at temperatures where both channels have similar contributions. The two lines shown for the total lattice thermal conductivity represent the upper-and lower-limit of the calculation, stemming from a slight anisotropy of the orthorhombic structure (Figure b, c, for detail see Supplemental Note 9). This observation is supported by the reported single-crystal thermal conductivity analysis of Ag8SnSe6, which found a comparable anisotropy in thermal conduction at 300 K. It should be emphasized that the conclusion that the diffuson channel dominates is independent of the form of the analytical scattering functions. Corresponding results utilizing a simplified phonon-phonon scattering term are shown in the Supporting Information (Supplemental Note 9).