Tunable Thermal Expansion Behavior in the Intermetallic YbGaGe
  We investigate the effects of carbon and boron doping on the thermal expansion in the hexagonal (P63/mmc) intermetallic YbGaGe. X-ray powder diffraction was used to measure the lattice constants on pure and doped (C or B at nominal levels of 0.5 %) samples from T~10 K to T~300 K. Also measured were resistivity, specific-heat, and magnetic susceptibility. While the pure YbGaGe samples exhibit positive thermal volume expansion, (V300K-V10K)/V300K = 0.94%, the volume expansion in the lightly C and B-doped samples, contract and tend towards zero volume expansion. Such a strong response with such light doping suggests that the underlying mechanism for the reported zero volume expansion is substitutional disorder, and not the previously proposed valence fluctuations. 
F. R. Drymiotis, Y. Lee, G. Lawes, J. C. Lashley, T. Kimura, S. M.   Shapiro, A. Migliori, V. Correa and R. A. Fisher