  A system of segregated boundary-domain integral equations (BDIEs) is obtained
from the Dirichlet problem for the diffusion equation in non-homogeneous media
defined on an exterior two-dimensional domain. We use a parametrix different
from the one employed by in (Dufera, 2019). The system of BDIEs is formulated
in terms of parametrix-based surface and volume potentials whose mapping
properties are analysed in weighted Sobolev spaces. The system of BDIEs is
shown to be equivalent to the original boundary value problem and uniquely
solvable in appropriate weighted Sobolev spaces suitable for infinite domains.
