For many Heusler compounds a spin polarisation close to 100% was predicted by band structure calculations. Thus if those materials are incorporated in magnetic tunnel junctions, a huge magnetoresistance is expected. However, employing AlOx tunneling barriers large effects could only be obtained with very few materials (e. g. Co2MnSi). Most Heusler materials, including the compound which is to be investigated in the proposed beam time, show only moderate magnetoresistance effects. A possible explanation is a reduced spin polarisation at the Heuser compound / AlOx interface, which may be seen as a reduced magnetization near the interface. Using the capabilities of the polarised neutron technique we will characterise the interfacial magnetization in this technologically relevant system.