Recently a new family of Cr-based A 2 Cr 3 As 3 (A = K, Rb, Cs) superconductors were reported, which own a rare quasi-one-dimensional (Q1D) crystal structure with infinite (Cr 3 As 3 ) 2chains and exhibit intriguing superconducting characteristics possibly derived from spin-triplet electron pairing. The crystal structure of A 2 Cr 3 As 3 is actually a slight variation of the hexagonal TlFe 3 Te 3 prototype although they have different lattice symmetry. Here we report superconductivity in a 133-type KCr 3 As 3 compound that belongs to the latter structure. The single crystals of KCr 3 As 3 were prepared by the deintercalation of K ions from K 2 Cr 3 As 3 crystals which were grown from a high-temperature solution growth method, and it owns a centrosymmetric lattice in contrast to the non-centrosymmetric K 2 Cr 3 As 3 .After annealing at a moderate temperature, the KCr 3 As 3 crystals show bulk superconductivity at 5 K revealed by electrical resistivity, magnetic susceptibility and heat capacity measurements. The discovery of this KCr 3 As 3 superconductor provides a different structural instance to study the exotic superconductivity in these Q1D Cr-based superconductors.

Abstract:Here we report the preparation and superconductivity of the 133-type Cr-based quasi-one-dimensional (Q1D) RbCr 3 As 3 single crystals.

A quaternary compound Bi 3 O 2 S 2 Cl, which consists of novel [BiS 2 Cl] 2layers, is reported. It adopts a layered structure of the space group I4/mmm (No. 139) with lattice parameters: a = 3.927(1) Å, c = 21.720(5) Å. In this compound, bismuth and chlorine atoms form an infinite planar layer, which is unique among the bismuth halides. Superconductivity is observed in both polycrystals and single crystals, and is significantly enhanced in the samples prepared with less sulfur or at higher temperatures. By tuning the content of sulfur, Bi 3 O 2 S 2 Cl can be converted from a semiconductor into a superconductor. The superconducting critical temperature ranges from 2.6 K to 3.5 K. Our discovery of the [BiS 2 Cl] 2layer opens another door in searching for the bismuth compounds with novel physical properties.