Abstract While the ultra‐low velocity zones (ULVZs) may hold key information about deep Earth dynamics, their elusive state and origin remain enigmatic. Recent high‐pressure experiments suggest that ULVZs may originate from the B2 FeSi crystallization from the outer core. Understanding the conductivity of the B2 phase can shed light on its role in deep mantle dynamics and serve as a test for its presence at the core‐mantle boundary (CMB). Here, we calculated the thermal and electrical conductivities of B2 Fe1‐xSix at 127 GPa and up to 4,500 K using first‐principles molecular dynamics. Our results show that under CMB conditions, the thermal and electrical conductivities of B2 FeSi are significantly higher than those of lower‐mantle minerals. The exceptionally high conductivities of B2 FeSi would enhance heat transfer and elevate temperatures within ULVZs, if B2 FeSi is present, thereby promoting the core dynamo and powering hotspots, consistent with seismic observations of ULVZs.