Normal-state transport and magnetic properties ofRNi2B2C(R=Y,Ho,La)

Magnetic susceptibility, resistivity, thermoelectric power, and Hall effect measurements have been made for $R{\mathrm{Ni}}_2{\mathrm{B}}_2\mathrm{C}$, $R=\mathrm{Y},\mathrm{H}\mathrm{o},\mathrm{L}\mathrm{a}$. The Y and Ho containing compounds are superconducting, with transition temperatures of 15 and 7.5 K, respectively. The La containing compound is nonsuperconducting down to 1.5 K. A distinct linear term is seen in the susceptibility of Y${\mathrm{Ni}}_2$ ${\mathrm{B}}_2$C, which is not seen in the nonsuperconducting La${\mathrm{Ni}}_2$ ${\mathrm{B}}_2$C. The two superconducting compounds have a linear resistivity at high temperatures, with a definite downward curvature below 300 K, while that of La${\mathrm{Ni}}_2$ ${\mathrm{B}}_2$C is linear up to 600 K (the limits of this study.) There seems to be an extra scattering process in the superconducting compounds which freezes out below 300 K. The thermopowers of the two superconducting compounds are identical, being small and negative, while that of La${\mathrm{Ni}}_2$ ${\mathrm{B}}_2$C is also negative, but is greater in magnitude. Analysis of the thermopower data reveals that La${\mathrm{Ni}}_2$ ${\mathrm{B}}_2$C has a factor of 2 larger electron diffusion term than the Y and Ho containing compounds, and that the latter values are nearly a factor of 10 smaller than expected from band theory. The Hall coefficient for all three materials is negative, small and shows some temperature dependence. At 300 K the carrier density for Y${\mathrm{Ni}}_2$ ${\mathrm{B}}_2$C is estimated to be 1.7 electrons per formula unit.