Superconductivity in the complex metallic alloy β − Al 3 Mg 2

Transport and thermodynamic properties were studied for the complex metallic compound $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Al}}_{3}{\mathrm{Mg}}_{2}$, composed of 925 atoms per unit cell. $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Al}}_{3}{\mathrm{Mg}}_{2}$ exhibits bulk superconductivity below ${T}_{c}=0.87\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. An exponential temperature dependence of the specific heat well below ${T}_{c}$ indicates BCS-like behavior with a nodeless gap of width ${\ensuremath{\Delta}}_{\mathit{BCS}}(0)\ensuremath{\approx}1.5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The coherence length is derived as ${\ensuremath{\xi}}_{0}=4.85\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\phantom{\rule{0.3em}{0ex}}\mathrm{m}$ and the Ginzburg Landau parameter ${\ensuremath{\kappa}}_{\mathrm{GL}}\ensuremath{\approx}13$, characterizing $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Al}}_{3}{\mathrm{Mg}}_{2}$ as a type II superconductor. Superconductivity in $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Al}}_{3}{\mathrm{Mg}}_{2}$ occurs in the absence of inversion symmetry of the crystal. Surprisingly, in spite of the rather complex crystal structure of $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Al}}_{3}{\mathrm{Mg}}_{2}$, physical properties turn out to be quite simple.