Study of superconductivity and antiferromagnetism in La<SUB>2-x</SUB>Nd<SUB>x</SUB>Rh<SUB>3</SUB>Si<SUB>5</SUB> system

It is well-known that the ternary rare earth silicides of the type R<SUB>2</SUB>Fe<SUB>3</SUB>Si<SUB>5</SUB> exhibit interesting superconducting and magnetic properties. Unlike R<SUB>2</SUB>Fe<SUB>3</SUB>Si<SUB>5</SUB> which forms in the tetragonal (space group P4/mnc) structure, R<SUB>2</SUB>Fe<SUB>3</SUB>Si<SUB>5</SUB> forms in the orthorhombic (Ibram or Iba2) structure. In this work, we establish the bulk superconductivity (T<SUB>c</SUB> = 4.4 K) and bulk antiferromagnetism (T<SUB>N</SUB> = 2.7 K) in La<SUB>2</SUB>Rh<SUB>3</SUB>Si<SUB>5</SUB> and Nd<SUB>2</SUB>Rh<SUB>3</SUB>Si<SUB>5</SUB>, respectively, from resistivity, susceptibility and heat-capacity studies. The heat-capacity data of Nd<SUB>2</SUB>Rh<SUB>3</SUB>Si<SUB>5</SUB> reveal significant presence of crystal-field contributions. These results are compared with the heat-capacity study of Gd<SUB>2</SUB>Rh<SUB>3</SUB>Si<SUB>5</SUB> which shows bulk antiferromagnetic ordering below 8.5 K. We have also analyzed the variation of T<SUB>c</SUB> with Nd substitution in the La<SUB>2-x</SUB>Nd<SUB>x</SUB>Rh<SUB>3</SUB>Si<SUB>5</SUB> system