of the structure factor for the wave vector corresponding to a leaf of the right clover on warming (triangles) and on cooling (squares). []{data-label="figure10"}](fig10){width="7cm"}

The diffracted intensities of a spot in the ordered phase was calculated for ${\bf k}_f$ fulfilling the condition of constructive interference and also for vectors from a very small surroundings of ${\bf k}_f$. Then maximal value of S were chosen to represent the intensity of spot at this ${\bf k}_f$. We use such procedure because the surface does not consist of ideal flat {211} facets during warming up and cooling processes, therefore spots can change shapes, intensities, and positions. The diffracted intensities of spots of faceted phase are different because areas of facets of different orientation are not equal. Moreover, their dependence on temperature during warming the system shows irregular behaviour (see Fig. \[figure10\]) because of facets grow i.e., from several small facets a bigger one arises. We observe rapid growth of S at temperature $T\approx 0.9$ when large pyramids are formed on the surface. During the cooling cycles, the S reaches nearly maximal value just below transition temperature what confirms formation of large {211} facets. The maximal values of S in the faceted phase are 