Susceptibility of the Rare Earth Ternary RNiSi$\text{}_{2}$ and RNiGe$\text{}_{2}$ Compounds

The ternary silicides and germanides RNiX$\text{}_{2}$ (R - rare earth, X = Si or Ge) with the orthorhombic CeNiSi$\text{}_{2}$-type structure are investigated by magnetometric measurements. CeNiSi$\text{}_{2}$, CeNiGe$\text{}_{2}$ and SmNiGe$\text{}_{2}$ have a nonmagnetic state in low temperatures. The compounds with R = Pr and Nd are ferromagnets while those containing R = Gd-Er are antiferromagnets. The de Gennes scaling of the Néel temperatures indicates a strong influence of the crystalline-electric field effects.