The phenomenological theory of complex interplay of superconductivity and magnetism in Ho 1-xDy xNi 2B 2C by Doh et al (1999 Phys.Rev.Lett. 83 5350) is based on the multi-band picture with at least one band which is strongly dominated by Ni3d-electron orbitals. These orbitals are insensitive to the antiferromagnetic order of the (Ho, Dy)4f-electrons, found in these alloys. In the present study we show by detailed analysis of the band structure that indeed such a band can be identified. This provides a microscopic justification of the basic idea underlying the phenomenological discussion.