  In this work, we present a subdomain discontinuous least-squares (SDLS)
scheme for neutronics problems. Least-squares (LS) methods are known to be
inaccurate for problems with sharp total-cross section interfaces. In addition,
the least-squares scheme is known not to be globally conservative in
heterogeneous problems. In problems where global conservation is important,
e.g. k-eigenvalue problems, conservative treatment must be applied. We, in this
study, proposed a SDLS method that retains global conservation. Such a method
resembles the LS formulation in each subdomain without material interface and
differs from LS in that an additional least-squares interface term appears for
each interface. Scalar flux is continuous in each subdomain with continuous
finite element method (CFEM) while discontinuous on interfaces for every pair
of contiguous subdomains. SDLS numerical results are compared with those
obtained from other numerical methods with test problems having material
interfaces. High accuracy of scalar flux in fixed-source problems and
$k_\mathrm{eff}$ in eigenvalue problems are demonstrated.
