Superconductivity in ternary Mg${}_4$Pd${}_7$As${}_6$

Abstract

We report the synthesis and characterization of a new compound Mg${}_4$Pd${}_7$As${}_6$, which was found to be a superconductor with $T_c=5.45$~K. Powder X-ray diffraction confirms the U${}_4$Re${}_7$Si${}_6$ structure (space group $Im$-$3m$, no. 229) with the lattice parameter $a$ = 8.2572(1)~Å. Magnetization, specific heat, and electrical resistivity measurements indicate that it is a moderate-coupling ($\lambda =0.72$) type-II superconductor. The electronic and phonon structures are calculated, highlighting the importance of antibonding Pd-As interactions in determining the properties of this material. The calculated electron-phonon copling parameter $\lambda =0.76$ agrees very well with the experimental finding, which confirms the conventional pairing mechanism in Mg${}_4$Pd${}_7$As${}_6$.

11 pages, 11 figures