Fig. 2: Two coexisting signals in reciprocal space.

a Reconstructed diffraction signals (see text and c) in the \([H,0,L]\) plane at various temperatures. Each image’s field of view is sufficiently large (note the larger field of view of the 23 K data set) to include the maxima of both peaks, enabling reliable extraction of their intensities. Ring-like patterns are due to incomplete background subtraction, and not related to presence of any impurity phases in our sample. b Momentum-space trajectory of the two peak centers indicated at the bottom of a. c Schematics of momentum scan (see text) in real and reciprocal space. The inset displays how the \((H,K,L)\) volume data were reconstructed and the \((H,0,L)\) slice extracted. d Temperature dependence of the intensities of the sharp and broad peaks, determined from two-dimensional fits to the data (Supplementary Fig. 2). Lines are guide to the eye. e, f Temperature evolution of the momentum centoids of the broad and sharp peaks, projected along \(L\) and \(H\) directions, respectively. A leveling off is seen below ~56 K for the sharp peak. While the relative momentum changes can be determined quite precisely, there is a systematic uncertainty in the absolute readings of \(L\) and \(H\) caused by imperfect determination of the sample’s orientation matrix, which we estimate to be 0.002 and 0.001 r.l.u., respectively. g, h Temperature evolution of the full width at half maximum (FWHM) of the sharp peak in \(L\) and \(H\), respectively. Horizontal shaded stripes indicate the FWHM (and its uncertainty) of the broad peak, which is weakly \(T\) dependent.