title: Anomalous reduction of the Lorenz ratio at the quantum critical point in YbAgGe.
abstract: We report measurements of the electrical and thermal transport on the hexagonal heavy-fermion metal YbAgGe for temperatures T ≥ 40  mK and in magnetic fields H∥ab up to 14 T. This distorted kagome-lattice system displays a series of magnetic states and a quantum critical point at H(c) = 4.5  T. The Lorenz ratio L(T)/L0 displays a marked reduction only close to H(c). A T-linear contribution below 120 mK, present at all different fields, allows us to extrapolate the Lorenz ratio towards T = 0. At the critical field this yields L/L0 = 0.92±0.03, suggesting a violation of the Wiedemann-Franz law due to strong inelastic scattering.
authors.affiliation: I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany.
authors.forename: J K
authors.initials: JK
authors.lastname: Dong
authors.forename: Y
authors.initials: Y
authors.lastname: Tokiwa
authors.forename: S L
authors.initials: SL
authors.lastname: Bud'ko
authors.forename: P C
authors.initials: PC
authors.lastname: Canfield
authors.forename: P
authors.initials: P
authors.lastname: Gegenwart