By far the greatest structural variety of rare-earth compounds is revealed in interstitially stabilized cluster complexes, predominantly of the elements scandium, yttrium, lanthanum and gadolinium. In contrast, cluster complexes of dysprosium, holmium and erbium have not been investigated thoroughly, yet. Hence, this thesis is intended to broaden the knowledge of interstitially stabilized cluster halides of dysprosium, holmium and erbium in terms of structure and electronic situation. The latter gives new insights into the bonding situation by means of band structure calculations, ...