Peierls-type structural phase transition in the low-dimensional superconductor Sc3CoC4

We provide information about the progression of the structurally low-dimensional superconductor ${\mathrm{Sc}}_{3}{\mathrm{CoC}}_{4}$ from its high-temperature phase to its Peierls-type distorted low-temperature phase. Results from inelastic x-ray scattering, diffuse scattering, and high-resolution x-ray diffraction experiments provide conclusive evidence that the onset of a modulation in the atomic positions during the structural transition is primarily driven by a combination of phonon softening and order-disorder transition. The completion of the phonon softening process at $\ensuremath{\sim}150$ K is found to be followed by two additional stages, i.e., an accumulation of gradual structural changes between 150 and 80 K and their saturation into the final low-temperature phase structure below $\ensuremath{\sim}80$ K.