YbGaGe: normal thermal expansion
  We report evidence of the absence of zero thermal expansion in well-characterized high-quality polycrystalline samples of YbGaGe. High-quality samples of YbGaGe were produced from high-purity starting elements and were extensively characterized using x-ray powder diffraction, differential thermal analysis, atomic emission spectroscopy, magnetization, and neutron powder diffraction at various temperatures. Our sample melts congruently at 920 C. A small amount of Yb2O3 was found in our sample, which explains the behavior of the magnetic susceptibility. These observations rule out the scenario of electronic valence driven thermal expansion in YbGaGe. Our studies indicate that the thermal expansion of YbGaGe is comparable to that of Cu. 
Y. Janssen, S. Chang, B.K. Cho, A. Llobet, K.W. Dennis, R.W. McCallum,   R.J. Mc Queeney, P.C. Canfield