## 3 Results  
A long-range ordering phenomenon can be observed in NiCoMnAl multilayer systems as can be seen in Figure 2a,b. The intended layered structure is cancelled, and transformed into a checkerboard-like periodic arrangement of darker and brighter areas. The pattern consists of three types of fields: big quadratic dark fields, smaller quadratic dark fields and in between slightly rectangular brighter fields.  
Figure 1: **(a)** The chosen compositions result in completely separated thermal hystereses for the active (blue) and intercalation layers (red). **(b)** Illustration of the sample system with 13 martensitic intercalations.  
Figure 2: TEM images of a cross section show a 3D-checkerboard structure (**a,b**). **(c)** EFTEM thickness map. **(d)** STEM dark field image of the checkerboard sample with the overlaid EDX elemental mappings. The scanned area is marked by the green rectangle. **(e)** Corresponding line profiles of the elemental compositions. **(f)** EDX line profiles of the Co content extracted from EDX mappings measured on three different regions across the whole lamella. The layer modulation in the Co content is clearly visible.  
The square regions are oriented at an angle of (45 \(\pm\) 2)\({}^{\circ}\) to the substrate. The geometric dimensions of the larger dark squares measure (60 \(\pm\) 5) nm and (35 \(\pm\) 3) nm for the smaller dark squares, while for the brighter rectangular fields (60 \(\pm\) 5) nm \(\times\) (35 \(\pm\) 3) nm have been determined. In the darker fields strong Moire patterns emerge, indicating that at least two different crystal lattices are on top of each other. The direction of the Moire patterns gives information about the orientation of the underlying crystal lattices [29].  
A relative thickness map was recorded using energy filtered TEM. The measurement was carried out with an energy window of 30 eV and showed no relevant patterned thickness variations that could explain this novel microstructure (see Figure 2c). From the measured 1.5-2.1 mean free path the thickness of the lamella has been determined to be about 90 nm in the thinnest surface region and up to 200 nm in the thickest parts near to the substrate. Furthermore, EDX mappings have been carried out to rule out a modulation of the elemental composition as reason for this special structure (see Figure 2d-f). The elemental composition has been checked by taking line profiles on different positions. An example of a line profile is given in Figure 2e). Here, only a modulation of the Co content of about 2% have been observed. For a better visibility only the EDX line profiles of Co are shown in Figure 2f measured across three different positions on the lamella. The clear modulation of the Co signal follows the sputtered layers of the appointed different compositions. The layers with higher Co content are found to be (49.4 \(\pm\) 8.2) nm, those with less Co content show a width of (32.9 \(\pm\) 8.2) nm, which fits well to the projected thicknesses for the active and intercalation layers. Thus, chemically the sample still consists of the intended layers of slightly varying composition and the checkerboard pattern has its origin in the crystalline structure.  
This is confirmed by dark field (DF) imaging using different diffraction spots. In Figure 3 SAED pattern of a part of the checkerboard are shown. The particular diffraction spots used for the corresponding DF images are marked by oranges circles. As can be seen from the DF images, the two most excited diffraction spots next to the central spot correspond to rectangular checkerboard fields rotated by 90\({}^{\circ}\) (Figure 3a,b) and can be considered to be austenite. A less strongly excited spot corresponds to all the greater squared fields (Figure 3c) and might be associated with a martensite lattice.