${\mathrm{Mo}}_3{\mathrm{Sb}}_7$ single crystals lightly doped with Cr, Ru, or Te are studied in order to explore the interplay between superconductivity, magnetism, and the cubic-tetragonal structural transition. The structural transition at 53 K is extremely sensitive to Ru or Te substitution which introduces additional electrons, but robust against Cr substitution. No sign of a structural transition was observed in superconducting ${\mathrm{Mo}}_{2.91}{\mathrm{Ru}}_{0.09}{\mathrm{Sb}}_7$ and ${\mathrm{Mo}}_3{\mathrm{Sb}}_{6.975}{\mathrm{Te}}_{0.025}$. In contrast, 3 at.$\%$ Cr doping only slightly suppresses the structural transition to 48 K while leaving no trace of superconductivity above 1.8 K. Analysis of magnetic properties suggests that the interdimer interaction in ${\mathrm{Mo}}_3{\mathrm{Sb}}_7$ is near a critical value and essential for the structural transition. All dopants suppress the superconductivity of ${\mathrm{Mo}}_3{\mathrm{Sb}}_7$. The tetragonal structure is not necessary for superconductivity.

• Received 26 May 2015
• Revised 20 July 2015

DOI:https://doi.org/10.1103/PhysRevB.92.064507