Heusler compounds are of great interest for various applications, since they are predicted to be half-metallic materials with full spin polarization of ~6.0 μB. However, the spin polarization experimentally found at finite temperatures is well below the predicted values. A reason may be electron-magnon interactions. We therefore propose to study the magnon dispersion relation in the complex reference material Co2FeSi, in complement to previous studies on the half-metallic ferromagnet NiMnSb.