Drastic annealing effects in transport properties of single crystals of the ${\mathrm{YbNi}}_2{\mathrm{B}}_2\mathrm{C}$ heavy fermion system

We report temperature-dependent resistivity, specific heat, magnetic susceptibility, and thermoelectric power measurements made on the heavy fermion system ${\mathrm{YbNi}}_2{\mathrm{B}}_2\mathrm{C},$ for both as-grown and annealed single crystals. Our results demonstrate a significant variation in the temperature-dependent electrical resistivity and thermoelectric power between as-grown crystals and crystals that have undergone optimal (150 h, $950°\mathrm{C})$ annealing, whereas the thermodynamic properties $\left[c_p\mathrm{}\right(T)\mathrm{}$ and $\chi \mathrm{}\left(T\right)\mathrm{}]$ remain almost unchanged. We interpret these results in terms of redistributions of local Kondo temperatures associated with ligandal disorder for a small $(\sim 1\%)$ fraction of the Yb sites.