  We propose a model of nodal order parameters for the superconducting A and B
- phase of skutterudite PrOs_4Sb_{12} and discuss the associated angular
dependent magnetothermal conductivity at low temperatures. The model for the
hybrid gap functions \De(k) containing an s- and g- wave parts is consistent
with recent thermal conductivity experiments in PrOs_4Sb_12. In particular the
model accounts for the data on polar an azimuthal field angle dependence of
\kappa_zz(\theta,\phi). The low temperature behaviour of thermodynamic
properties in zero field is also presented. We show that the effect of impurity
scattering on a nodal hybrid gap function immediately leads the opening of a
gap and related exponential behaviour of low temperature specific heat and
thermal conductivity which is very different from d- wave superconductors.
