Correction to: Nature Physics https://doi.org/10.1038/s41567-018-0232-7, published online 6 August 2018.

In the version of this Article originally published, the expression for Pc was missing a division slash; it should have read \(P_{\mathrm{c}} = \pm 2d_yd_z/(d_y^2 + d_z^2) \approx \pm \frac{2}{3}\it{\Delta} _{{\mathrm{h}},{\mathrm{F}}}/\it{\Delta} _{1{\mathrm{h}}}\). Also, affiliation 5 was missing ‘Institute of Physics’; it should have read ‘International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, Warsaw, Poland’. These issues have now been corrected.