Search for unconventional superconductors among the YTE 2Si2 compounds (TE = Cr, Co, Ni, Rh, Pd, Pt)

Abstract

Motivated by the recent discovery of exotic superconductivity in YFe₂Ge₂ we undertook reinvestigation of formation and physical properties of yttrium-based 1:2:2 silicides. Here we report on syntheses and crystal structures of the YTE ₂Si₂ compounds with TE = Cr, Co, Ni, Rh, Pd and Pt, and their low-temperature physical properties measurements, supplemented by results of fully relativistic full-potential local-orbital minimum basis band structure calculations. We confirm that most of the members of that family crystallize in a tetragonal ThCr₂Si₂-type structure (space group I4/mmm) and have three-dimensional Fermi surface, while only one of them (YPt₂Si₂) forms with a closely-related primitive CaBe₂Ge₂-type unit cell (space group P4/nmm) and possess quasi-two-dimensional Fermi surface sheets. Physical measurements indicated that BCS-like superconductivity is observed only in YPt₂Si₂ (T _c = 1.54 K) and YPd₂Si₂ (T _c = 0.43 K), while no superconducting phase transition was found in other systems at least down to 0.35 K. Thermal analysis showed no polymorphism in both superconducting phases. No clear relation between the superconductivity and the crystal structure (and dimensionality of the Fermi surface) was observed.