Tuning competing ordering mechanisms with hydrostatic pressure in the $4d$ intermetallic compound ${\mathrm{Mo}}_3{\mathrm{Sb}}_7$ reveals an intricate interplay of structure, magnetism, and superconductivity. Synchrotron x-ray diffraction and magnetic susceptibility measurements, both employing diamond anvil cell technologies, link a first-order structural phase transition to a doubling of the superconducting transition temperature. In contrast to the spin-dimer picture for ${\mathrm{Mo}}_3{\mathrm{Sb}}_7$, we deduce from x-ray absorption near-edge structure and dc magnetization measurements at ambient pressure that ${\mathrm{Mo}}_3{\mathrm{Sb}}_7$ should possess only very small, itinerant magnetic moments. The pressure evolution of the superconducting transition temperature strongly suggests its enhancement is due to a difference in the phonon density-of-states with changed crystal symmetry.

• Received 5 August 2016
• Revised 4 January 2017

DOI:https://doi.org/10.1103/PhysRevB.95.125102