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Abstract

The robust field-insensitive heavy fermion features in Sm-3 Ru-4 Ge-13 and the magnetic phase transition at T-N approximate to 5 K are studied using magnetization M(T), specific heat C-p(T), resistivity rho(T) and thermal conductivity k(T)(T). The average crystal structure of Sm-3 Ru-4 Ge-13 conforms to the cubic space group Pm (3) over barn however, signatures of subtle structural distortions are obtained from the x ray data. The magnetic susceptibility, chi(T), follows a modified CurieeWeiss law indicating the presence of crystal fields of Sm3+ and the significance of van Vleck terms. No sign of ferromagnetism is observed in M(H) of Sm-3 Ru-4 Ge-13 which yields only 0.025 mu(B)/f.u.-Sm at 2 K, 7 T. The Sommerfeld coefficient, gamma approximate to 220 mJ/mol-Sm K-2, estimated from the analysis of low temperature specific heat suggests the formation of heavy quasi particles at low temperature. Though a lnT dependence of rho(T) is observed till 60 K, the resistivity behavior is accounted for by assuming a two-band model for activated behavior of charge carriers. The field scans of resistivity, rho(H), below TN display significant nonlinearity while those above the TN are more metal-like. Low values of thermal conductivity, kappa(T)(T), are observed in Sm-3 Ru-4 Ge-13 however, displaying an anomaly at T-N which signifies magnetoelastic coupling. A fairly high value of Seebeck coefficient, S approximate to 40 mu V/K is observed at 300 K. We identify Sm-3 Ru-4 Ge-13 as a low charge carrier density system with unusual field-insensitive heavy fermion features very similar to the filled skutterudites. (C) 2016 Elsevier B.V. All rights reserved.