We find that ${\mathrm{CePtSi}}_2$ crystallizes in the ${\mathrm{CeNiSi}}_2$-type orthorhombic structure with lattice parameters a=0.4288(2) nm, b=1.6718(4) nm, and c=0.4238(2) nm. The magnetic resistivity data show that the Ce in ${\mathrm{CePtSi}}_2$ has a doublet ground state according to the theory of Cornut and Coqblin. Above 100 K the inverse molar magnetic susceptibility follows a Curie-Weiss law, leading to an effective moment of 2.56${\mathrm{\mu }}_{\mathit{B}}$ per cerium atom and a paramagnetic Curie temperature of -17 K. Down to 70 mK no sign of a transition into a state of long-range magnetic order or a superconducting state was detected by ac susceptibility measurements. The coefficient of the electronic specific heat has a maximum of about 1700 mJ/mol ${\mathrm{K}}^2$ at 1.25 K.

• Received 2 July 1990

DOI:https://doi.org/10.1103/PhysRevB.42.6542