The coexistence of the superconductivity and magnetism in the Ho1-xDyxNi2B2
C is studied by using Ginzburg-Laudau theory. This alloy shows the coexiste
nce and complex interplay of superconducting and magnetic order. We propose
a phenomenological model which includes two magnetic and two superconducti
ng order parameters accounting for the multiband structure of this material
. We describe phenomenologically the magnetic fluctuations and order and de
monstrate that they lead to anomalous behavior of the upper critical field.
The doping dependence of T-c in Ho1-xDyxNi2B2C showing a reentrance behavi
or is analyzed yielding very good agreement with experimental data.