Enormous electron-electron scattering in the filled-cage cubic compound B a10 T i24 B i39

The cubic intermetallic compound Ba10Ti24Bi39 has a Ba6Bi16 polyhedral cage with a Bi guest atom encapsulated inside. The compound can be formulated as Ba5Ti12Bi19+x when x signifies the extra Bi atoms filling cages. It crystallizes in a complex noncentrosymmetric cubic structure in space group P-43m with cell parameter a=12.6787(4)Å. The guest Bi atoms distribute diffusely in the cages and seem to play a role in stabilizing the crystal structure. The magnetic susceptibility of this compound shows a weak temperature dependence with a positive slope coefficient. The charge transport properties as a function of temperature exhibit two competing components which are in charge of positive and negative magnetoresistances. Electronic band-structure calculations reveal the complex multiband hybridization of Ti/Bi orbitals near the Fermi surface, which may play a role in the enormous electron-electron scattering in this material evidenced by the large Kadowaki-Woods ratio.