NMR as a Probe of Band Inversion in Topologically Nontrivial Half-Heusler Compounds

209 Bi nuclear magnetic resonance (NMR) was studied in half-Heusler compounds YPdBi and YPtBi. The observed NMR spectra exhibit low intensity because of short nuclear transverse relaxation time ( T 2 ) governed by sizable structural disorder. In both compounds, the frequency shift of the 209 Bi bulk nuclei is dominated by the chemical shielding (δ cs ) contribution. Remarkably, it is positive for topologically trivial YPdBi yet strongly negative for topologically nontrivial YPtBi. At the same time, the spin–lattice relaxation rate (1/ T 1 ) is distinctly larger in YPtBi due to stronger spin–orbit coupling and postulated inversion of the electronic bands near the Fermi level. The unique features of δ cs and 1/ T 1 established for YPtBi can be considered as possibly universal fingerprints of topologically nontrivial state in similar materials.