Fig. 4: Phase stability upon orthorhombic distortions.

Energy ΔE per formula unit as function of the orthorhombic distortion d at fixed unit cell volume and measured with respect to the C(xyyx) phase at d = 0 (T0 in Table 1). We compare C(xyyx) with the two nematic configurations C(xxxx) and C(yyyy) assuming a magnetic order C-AFS-a. Experimental data are taken from refs. ^19,25,51. The phases T0, T7, and T17 refer to Table 1, phases O0, O12, and O17 to Table 3.