Results of the refinements, in the $75^{\circ}-82^{\circ} 2 \theta$ and $98^{\circ}-106^{\circ} 2 \theta$ intervals, in $\mathrm{Na}_{0.5} \mathrm{K}_{0.5} \mathrm{NbO}_{3}$, at 2 K, using two different models with the monoclinic $P m$ and the rhombohedral $R 3 c$ space groups. The rhombohedral space group takes into account perfectly the observed splitting, unlike the monoclinic Pm.
Results of the refinements, in the 75^{\circ}-82^{\circ} 2 \theta and 98^{\circ}-106^{\circ} 2 \theta intervals, in \mathrm{Na}_{0.5} \mathrm{K}_{0.5} \mathrm{NbO}_{3}, at 2 K, using two different models with the monoclinic P m and the rhombohedral R 3 c space groups. The rhombohedral space group takes into account perfectly the observed splitting, unlike the monoclinic Pm.