Enormous electron-electron scattering in the filled-cage cubic compound Ba10Ti24Bi39

Abstract

The cubic intermetallic compound $\mathrm{B}{\mathrm{a}}_{10}\mathrm{T}{\mathrm{i}}_{24}\mathrm{B}{\mathrm{i}}_{39}$ has a $\mathrm{B}{\mathrm{a}}_{6}\mathrm{B}{\mathrm{i}}_{16}$ polyhedral cage with a Bi guest atom encapsulated inside. The compound can be formulated as $\mathrm{B}{\mathrm{a}}_{5}\mathrm{T}{\mathrm{i}}_{12}\mathrm{B}{\mathrm{i}}_{19+x}$ when $x$ signifies the extra Bi atoms filling cages. It crystallizes in a complex noncentrosymmetric cubic structure in space group $P\text{\ensuremath{-}}43m$ with cell parameter $a=12.6787(4)\phantom{\rule{0.16em}{0ex}}\AA{}$. 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.