Indications of a magnetic‐field‐driven anisotropy in the hybridization gap semiconductor CeOs 4 As 12

The filled skutterudite compound CeOs 4 As 12 displays phenomena that are associated with hybridization between the 4f‐electron and conduction‐electron states. This holds especially true for a semiconducting ground state with a main energy gap as small as Δ / k B  = 45 K. When subjected to magnetic field, the hybridization gap semiconductor CeOs 4 As 12 becomes metallic below around 2.5 K. Preliminary electrical‐resistivity experiments provide evidence for an anisotropy of magnetic‐field‐induced insulator–metal transition in this cubic material. Our findings suggest a contribution of the quartet $4{\rm f \hbox{-} }\Gamma _{67}^{- } $ states to transport properties of CeOs 4 As 12 .