Superconductivity in the C32 Intermetallic Compounds AAl(2-x)Si(x), with A=Ca and Sr, and 0.6<x<1.2

TL;DR

This paper investigates superconductivity in AAl(2-x)Si(x) compounds with A=Ca, Sr, and Ba, revealing new superconducting materials with transition temperatures up to 7.8 K and discussing their electronic properties.

Contribution

It reports the discovery of superconductivity in CaAlSi and SrAlSi, analyzes their composition-dependent transition temperatures, and compares their electronic characteristics to MgB2.

Findings

Superconductivity observed at 7.8 K in CaAlSi and 5.1 K in SrAlSi.

A Tc-peak at x=1 and a possible electronic transition at x~0.75.

Carriers are predominantly electrons, unlike holes in MgB2.

Abstract

The intermetallic compounds AAl2-xSix, where A = Ca, Sr or Ba, crystallize in the C32 structure, same as the recently discovered MgB2 with a high superconducting transition temperature of 39 K. For x = 1, superconductivity has been observed in AAlSi with A = Ca and Sr, but not with A = Ba. The transition temperatures are 7.8 and 5.1 K, respectively for CaAlSi and SrAlSi. The CaAl2-xSix compound system display a Tc-peak at x = 1, a possible x-induced electronic transition at x ~ 0.75 and a possible miscibility gap near x ~ 1.1 which results in a very broad superconducting transition. The Seebeck coefficients of AAlSi indicate that their carriers are predominantly electrons in nature, in contrast to the holes in MgB2.