Kondo effect in a novel 5d quasi-skutterudite Yb3Os4Ge13
  We report the crystal growth of a new compound, Yb3Os4Ge13, by using a Bi-flux method. X-ray diffraction measurement shows that it crystallizes in the quasi-skutterudite-type caged structure with a cubic space group of Pm-3n (No. 223). Magnetic measurements reveal almost fully localized Yb f-moments above 120 K. The resistivity exhibits a crossover from metallic to insulating behavior with a logarithmic increase below ~ 40 K. The specific heat coefficient shows a rapid upturn below ~5 K and exceeds 2 J mol-1 K-2 at 2 K. Our experimental analysis and electronic band structure calculations demonstrate that Yb3Os4Ge13 exhibits the Kondo effect due to strong hybridization of the localized Yb f-moments with the p-electrons of the surrounding Ge-cages. 
C.L. Yang, X. Wang, X. Zhang, D.S. Wu, M. Liu, P. Zheng, J.Y. Yao,   Z.Z. Li, Y.F. Yang, Y.G. Shi, J.L. Luo, N.L. Wang
cond-mat.str-el