SUPERCONDUCTIVITY AT 15-K IN THE METASTABLE SCNI2B2C COMPOUND

A superconducting transition around 15-16 K is reported for metastable , as-melted ScNi2B2C samples. Zero resistivity T(c)(zero) was observed at 14.6 K with T(c)(onset) around 16.5 K. A consistent diamagnetic T( c) signal was observed around 14.8-15.6 K. The new superconducting pha se was identified as isostructural to the quaternary LuNi2B2C-type pha se with tetragonal lattice parameters a = 3.34 angstrom and c = 10.2 a ngstrom. This superconducting phase is unstable due to the extremely s mall Sc3+ ionic size, where the Sc atom is located in the cavity forme d by the B-Ni-B-C network and no superconducting transition could be o bserved down to 5 K after 1050-degrees-C annealing.