  First principle FLAPW-GGA calculations have been performed with the purpose
to understand the peculiarities of band structure and Fermi surface topology
for recently discovered superconductor: Sr4V2Fe2As2O - in comparison with
isostructural phase Sr4Sc2Fe2As2O6. Our main finding is that the replacement of
Sc on vanadium leads to drastic transformation of electronic, magnetic and
conductive properties of these materials: as against non-magnetic
Sr4Sc2Fe2As2O6 which is formed from non-magnetic conducting [Fe2As2] and
insulating [Sr4Sc2O6] blocks, Sr4V2Fe2As2O6 consists from non-magnetic
conducting [Fe2As2] blocks and [Sr4V2O6] blocks which exhibit magnetic
half-metallic properties.
