Superconductivity and magnetism in the La<SUB>2-x</SUB>Nd<SUB>x</SUB>Rh<SUB>3</SUB>Si<SUB>5</SUB> system

It is now well known that the compounds that belong to the R2Fe2Si5 series exhibit unusual superconducting and magnetic properties. Although a reasonable number of studies have been made on this series, similar efforts on another series, namely, R2Rh3Si5, whose structure is closely related to R2Fe3Si5 have not been made. In this paper, we have established the bulk superconductivity in La2Rh3Si5 below 4.4 K and bulk antiferromagnetism in Nd2Rh3Si5 below 2.7 K, from resistivity, susceptibility, and heat-capacity studies. The superconducting transition temperature of (Tc) La2Rh3Si5 decreases with the Nd substitution for La and we have analyzed this Tc dependence using Abrikosov and Gor'kov theory with crystal-field contributions. The estimated value of the interaction between the conduction electrons and the rare-earth spin (Jsf) is 37 meV which is adequate to suppress the coexistence of superconductivity and antiferromagnetism in La2-xNdxRh3Si5 alloys above 0.6 K. Finally, we have also analyzed the temperature dependence of the upper critical field of Nd-doped La2Rh3Si5 alloys using a theory which incorporates spin-orbit coupling with an additional pair breaking parameter