## 1 Introduction  
Shape memory alloys reveal the fascinating ability to recover their initial shape after deformation upon heating. Therefore, their electrical and thermal properties depend strongly on temperature and mechanical stress, which opens different fields of applications [1; 2]. Their functional abilities originate in a temperature induced phase transition, known as martensitic transformation, between two crystal structures: the high-temperature austenite and the low-temperature martensite phase. The discovery of the shape memory effect in ferromagnetic Ni\({}_{2}\)MnGa by [PERSON] et al. in 1996 [3], offers new application fields of shape memory alloys, because the martensitic transition cannot only be triggered by temperature, mechanical strain or hydrostatic pressure but also by external magnetic fields [4; 5; 6; 7]. This so-called magnetic shape memory effect, e.g., allows much higher cycling frequencies of the phase transition compared to conventional thermally driven shape memory alloys, which are limited due to the thermal transport [8; 9]. A special class of magnetic shape memory alloys are Heusler compounds such as NiMnX (X = Al, Ga, Sn, In), which are considered as promising materials for magnetocaloric cooling applications due to their magnetoelastic coupling near room temperature [10; 11; 12]. However, most of the compounds show a large thermal hysteresis, which limits their potential in future applications [13; 14; 15]. Therefore, efficient mechanisms to change the martensitic transformation behavior have to be identified. In literature different approaches can be found to solve this issue ranging from the improvement of the chemical composition of the chosen material [16], the enhancement of the compatibility between martensitic and austenitic phase by applying a hydrostatic pressure [17] to just using the minor loops of the thermal hysteresis [18].  
In a previous study, we have demonstrated that the thermal hysteresis could be decreased by preparing off-stoichiometric NiCoMnAl multilayer systems, which consist of alternating grown martensite intercalations (MIs) and active transforming austenitic layers (ALs) [19]. This MIs have shown to be beneficial for transforming films, because the formation energy during martensite nucleation is reduced. The temperature dependent magnetization measurements have shown a significant decrease in hysteresis width as a function of the number of MIs. If the austenite active layers have a similar thickness compared to the martensite intercalations an extraordinary microstructure has been visualized in cross section images [19].  
Independently from the considered material, the applied treatment or the scale of the investigated structure, it is well known that the microstructure has a great impact on materials properties such as magnetic, electronic or mechanical behavior [20; 21; 22; 23; 24; 25; 26]. Therefore, effects of the observed structure on the properties of the shape memory alloy can be expected, but little is known about this novel structure so far. In the present study we investigate the microstructure of the arrangement by transmission electron microscopy (TEM) in terms of crystallinity, temperature dependence, influence of layer thicknesses and discuss its physical origin.