A previous calculation of the mathematical properties of a Kramers doublet for extrema of the mean $g$ value is extended to monoclinic symmetries. The theory is applied to the paramagnetic resonance data for La${\mathrm{F}}_3$: ${\mathrm{Yb}}^{3+}$. These data are shown to be consistent with a ${\mathrm{Yb}}^{3+}$ site of ${\mathrm{C}}_{2v}$ point symmetry.

• Received 14 May 1970

DOI:https://doi.org/10.1103/PhysRevB.2.2813