Structural signature of SP$\rightarrow$M$^\ast$ transition [#!KiryukhinPRB95!#]

Kiryukhin et al. observed the SP$\rightarrow$M$^\ast$ transition with high-resolution X-ray measurements; the superlattice Bragg reflection split at the ${\rm SP}-{\rm M}^\ast$ phase boundary, indicating an incommensurate modulation of the lattice dimerized state in the M$^\ast$ phase [153].