Antiferromagnetism in the Kondo lattice system Ce(Ni$_{0.25}$In$_{1.75})$.*

The pseudobinary compound Ce(Ni$_{0.25}$In$_{1.75})$, which crystallizes in a hexagonal AlB$_{2}$ type structure with space group P6/mmm, exhibits antiferromagnetic ordering below the temperature 3.9 K, as revealed in the magnetic susceptibility, electrical resistivity and low-temperature specific-heat data. A ln(T) dependence is seen in the high temperature region for the magnetic contribution to the resistivity $\rho _{m}$, which is one of the characteristic features of dense Kondo systems. The magnetic entropy S$_{m}$(T$_{N})$ associated with the magnetic structure of Ce(Ni$_{0.25}$In$_{1.75)})$ is found to be only 62{\%} of Rln(2), corresponding to a reduction of 38{\%} of the cerium moment. This large magnetic reduction may be able to be attributed to Kondo effect. The heat capacity C(T) of Ce(Ni$_{0.25}$In$_{1.75})$, in the paramagnetic state at temperatures between 8 and 20 K, can be fitted to the expression C$_{n}$ = $\gamma $T + $\beta $T$^{3}$ by a least squares analysis, which yields the value $\gamma $ = 123 mJ/mol K$^{2}$ and $\beta $ = 1.2 mJ/mol K$^{4}$, the latter value corresponding to the Debye temperature $\Theta _{D}$ = 169 K.