  Inelastic scattering processes typically introduce friction among carriers
and reduce the transport properties of photons, phonons, and electrons.
However, we predict that in contrast to the role in reducing thermal
conductivity, four-phonon scattering dominates near-field radiative heat
transfer (NFRHT) in both boron arsenide~(BAs) and boron antimonide. Including
four-phonon scattering results in a nearly 400-fold increase in the total heat
flux between two BAs thin-films compared to three-phonon scattering alone. This
non-intuitive enhancement arises from the large number of NFRHT channels
activated by four-phonon scattering outcompete the effect of decreased coupling
strength of surface phonon polaritons at the resonance frequency. Additionally,
we point out that four-phonon scattering to decrease NFRHT in certain other
systems.
