We report the thermal conductivity and specific heat of amorphous silicon thin films measured from 5-300 K using silicon-nitride membrane-based microcalorimeters. Above 50 K the thermal conductivity of thin-film amorphous silicon agrees with values previously reported by other authors. However, our data show no plateau, with a low T suppression of the thermal conductivity that suggests that the scattering of long wavelength, low Q vibrations goes as Q2. The specific heat shows Debye-like behavior below 15 K, with theta(D) = 487 +/- 5 K, and is consistent with a very small contribution of tunneling states in amorphous silicon. Above 15 K, the specific heat deviates less from Debye behavior than does its crystalline allotrope, indicating no significant excess modes (boson peak) in amorphous silicon.

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Physical behavior of several YbTM intermetallics has been studied by means of x-ray powder diffraction, magnetization, dc magnetic susceptibility, heat capacity, and electrical resistivity measurements. The compounds YbTBi with TϭCu, Ag, Au and YbTSn with TϭAg, Au, Zn were shown to be nonmagnetic due to the presence of divalent ytterbium ions. The bismuthide YbPdBi as well as the stannides YbRhSn and YbPtSn were found to exhibit localized magnetism of almost trivalent Yb ions. The electrical behavior of these three phases is characteristic of dense Kondo systems, and their low-temperature specific heat data indicate a possible heavy fermion ground state.

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