title: Low temperature transport properties and heat capacity of single-crystal Na8Si46.
abstract: The low temperature thermal conductivity, resistivity, and Seebeck coefficient of single-crystal Na(8)Si(46) are investigated revealing the intrinsic low temperature transport properties of this material. Metallic conduction is observed, with a higher residual resistance ratio than any other known type I clathrate. Heat capacity together with thermal conductivity provide insight into the Na disorder inside the polyhedra formed by the Si framework. Single-crystal structural refinement and thermal property analyses reveal anisotropic disorder for Na inside the tetrakaidecahedra due to a reduction in the symmetry inside these polyhedra, unlike that for Na inside the dodecahedra.
authors.affiliation: Department of Physics, University of South Florida, Tampa, FL 33620, USA.
authors.forename: S
authors.initials: S
authors.lastname: Stefanoski
authors.forename: J
authors.initials: J
authors.lastname: Martin
authors.forename: G S
authors.initials: GS
authors.lastname: Nolas