Fig. 3: Comparison between calculated and measured susceptibility.

a Susceptibility evaluated from the quasiparticle Hamiltonian as a function of temperature and a-axis strain, χ^qp(ε_aa, T). The susceptibility is resolved into contributions from the three t_2g orbitals. The critical (compressive) strain is close to ε_aa = − 0.50%. b Experimentally determined \({K}_{1^{\prime} \perp }^{{{{\rm{s}}}}}-{K}_{1| | }^{{{{\rm{s}}}}}\) as a function of temperature and applied stress, referenced to the critical stress ε_v. K^s denotes the spin part of the total shift. To calculate the difference continuously, shifts have been interpolated from Fig. 1 after subtraction of the known orbital contribution. (\({K}_{1| | }^{{{{\rm{o}}}}}=+0.18 \%\), \({K}_{1{\prime} \perp }^{{{{\rm{o}}}}}=0.0 \%\))⁴⁰. Error bars are determined by the average linewidth of the two sites. The inset on the right illustrates the Fermi-liquid crossover temperature as a function of uniaxial strain, extracted from our Knight-shift data. The defining criterion is the shift extremum separating the regimes of T-independent behavior, and that of logarithmic T-dependence. Error bars denote the temperature range in which the shift variation about the extremum is less than the linewidth.