Fe/FeSi/Si/FeSi/Fe epitaxial structures with combined spacers are prepared using co-evaporation. Combined spacers consist of Fe0.5Si0.5grown at elevated temperature and nominally pure Si. The thickness of each part of the combined spacers is varied from 0 to 20A. Magnetic properties are examined with longitudinal MAKE hysteresis and Brillouin light scattering. Inserting Fe0.5Si0.5layers at the bottom interface increases antiferromagnetic coupling due to the suppression of ferromagnetic coupling. Interlayer exchange coupling for combined spacers exceeds 8 erg/cm2. The dominant role of the insulating-type part of the combined spacer consisting of nominally pure Si spacers for strong antiferromagnetic coupling is demonstrated.