Anisotropic suppression of the phononic thermal conductivity by magnetic field in SmAlSi

We report the thermal and electrical conductivity data for the magnetic Weyl semimetal SmAlSi measured in a magnetic field ($B$) with two different orientations. In one case, $B$ was applied perpendicular to the heat or charge current; in the other they were parallel. For both configurations, the magnetic field affects the magnetic structure identically as $B$ is always parallel to the equivalent tetragonal axis. Our results indicate that phonon heat transport in response to the magnetic field exhibits strong anisotropy at low temperature: it appears to be independent of $B$ in the perpendicular configuration but is strongly suppressed in the parallel configuration. Understanding this unusual behavior can lead to designing better materials for thermoelectricity or directional heat switches.