On the ${}^{12}$C/${}^{13}$C carbon isotope effect in the quasi one-dimensional superconductor Sc${}_3$CoC${}_4$

Sc${}_3$CoC${}_4$ is the only superconductor in the group of the isotypic carbides Sc${}_{3}M$C${}_4$ ($M$ = Mn, Fe, Ru, Os, Co, Rh, Ir, Ni), rendering it into an ideal benchmark system to systematically study the prerequisites and mechanism of superconductivity in such quasi one-dimensional structures. To investigate the isotope effect, the substitution series Sc${}_3$Co(${}^{12}$C${}_{1-x}$${}^{13}$C${}_x$)${}_4$ with $x$ = 0, 0.5 and 1 was synthesized by arc melting. The sample homogeneity was confirmed by powder X-ray diffraction and NMR spectroscopy. The resulting isotope coefficient based on magnetization studies on polycrystalline samples and electrical resistivity measurements on single crystals of $\alpha$ = 0.58 lies close to the value of 0.5 predicted by BCS theory.