Fig. 1: Structure, composition and transport measurements of LuH2±xNy.

a, Powder XRD patterns of LuH2±xNy and Rietveld fitting curves (red lines) to the data. The tiny reflection at 32.2° can be indexed to the phase of Lu2O3. Inset, LuH2±xNy samples that exhibit a dark-blue colour. b, Comparison of XRD patterns with normalization of our sample SX1 to the data downloaded from ref. 1. Inset, enlarged view with 2θ from 29° to 37° for two of our samples (SX1 and SX5) and that from ref. 1. The main reflections of our samples seem to be sharper than those of ref. 1. c, SEM images and typical EDS of spot 1. Left inset, the image with 10 spots measured by point-wise measurement of EDS; right inset, the mapping image for nitrogen elements in another region. It is clear that the nitrogen distribution is not uniform in the sample, and it remains to be resolved at which positions these nitrogen atoms are located in the lattice. d, Temperature dependence of resistivity for three LuH2±xNy samples under ambient pressure. Inset, the image of the measured sample (S1) with electrodes attached at ambient pressure. The error bar for determining resistivity is about ±10%. The ρ–T curves are roughly linear from 60 K to 300 K and exhibit a power-law temperature dependence at lower temperatures (2–60 K). The red solid lines represent the fitting curves using ρ = ρ0 + ATn from 2 K to 60 K, where ρ0 is the residual resistivity and n and A are the fitting parameters. The fitting yields n = 2.89 and 2.71 for S2 and S3, respectively. a.u., arbitrary unit.