"Heusler compounds, with a general composition X2YZ (with X, Y being a transition metal and Z an element from the III-V groups) are attracting an interest due to their possible use in the novel field of spin-dependent devices, also known as spintronics. This interest in Heusler compounds comes from the half-metallic character of their spin-split band structure, i.e. metallic behavior for one spin component, and insulating behavior for the other one, as predicted by ab-initio calculations for many compounds of this material class. As such, these materials may exhibit a 100 % spin polarization at the Fermi level, which would make them ideal candidates for e.g. spin polarizers or spin detectors. An important force to be understood in detail in those materials is the spin-orbit coupling, which provides interaction between spin and the lattice. As such, the spin-orbit coupling is an underlying force for many important effects, such as Hall effect, spin Hall effect (and their inverse variants), spin diffusion length, Gilbert damping etc. Therefore, here we propose to investigate spin orbit coupling of the first and the second order in the Heusler compounds using optical and magneto-optical Kerr effect (MOKE) spectroscopy of the first (longitudinal MOKE) and the second (quadratic MOKE (QMOKE)). Furthermore, we want to investigate Heusler compounds using infrared (IR) spectroscopy and MOKE-IR spectroscopy, as those probe spin-orbit coupling in the vicinity of the Fermi level. Note that QMOKE spectroscopy has never been realized yet and that IR-MOKE is an unique technique in the world scale."