Influence of Anomalous Changes in the Crystal Structure on the Transport Properties of YbNiCuAl Series of Alloys.

Results of the transport properties of the YbNiCuAl (x = 0, 0.2, 0.5, 0.8 and 1.0) series of alloys are reported. The previous analysis of X-ray diffraction patterns indicates that all compounds crystallize in the hexagonal ZrNiAl structure with a linear behavior of the unit cell volume as a function of the Cu concentration (x). This is not found in the unit cell parameters, showing a discontinuity between x = 0.5 and 0.8. Such discontinuities affect the behavior of the electrical resistivity, in which the position of the minimum temperature changes from 95 K to 175 K, and a rise in the low temperature slope in the magnetic contribution (with -lnT dependence) from 21 μΩcm to 212 μΩcm is observed. In addition, the electronic coefficient of the specific heat increases almost twofold from 125 mJ/mol·K (x = 0.5) to 246 mJ/mol·K (x = 0.8). These changes are attributed to the variation of the distance between Yb and transition metals (Ni and Cu) along the series and the different electronic properties of the transition metals (Ni and Cu).