New superconducting and magnetic R-T-B-C systems (R = rare earth; T = Ni, Pd)

Our discovery of superconductivity in Y-Ni-B-C system (T<SUB>c</SUB>~12 K) has opened up a new field in superconductivity and magnetism in intermetallics. A brief description of the discovery of these new borocarbide materials is given. We have synthesised NdNi<SUB>2</SUB>B<SUB>2</SUB>C and GdNi<SUB>2</SUB>B<SUB>2</SUB>C for the first time and our measurements show that NdNi<SUB>2</SUB>B<SUB>2</SUB>C (T<SUB>m</SUB> ~5 K) and GdNi<SUB>2</SUB>B<SUB>2</SUB>C (T<SUB>m</SUB> ~19 K) undergo magnetic ordering. CeNi<SUB>2</SUB>B<SUB>2</SUB>C does not exhibit magnetic ordering down to 4.2 K; the magnitude of its magnetic susceptibility is consistent with Ce ions in mixed valence state. We comment on the magnetic properties of the two superconducting materials ErNi<SUB>2</SUB>B<SUB>2</SUB>C and LuNi<SUB>2</SUB>B<SUB>2</SUB>C