  We show the existence of an energetic solution to a quasistatic evolutionary
model of shape memory alloys. Elastic behavior of each material phase/variant
is described by polyconvex energy density. Additionally, to every phase
boundary, there is an interface-polyconvex energy assigned, introduced by M.
\v{S}ilhav\'{y}. The model considers internal variables describing the evolving
spatial arrangement of the material phases and a deformation mapping with its
first-order gradients. It allows for injectivity and orientation-preservation
of deformations. Moreover, the resulting material microstructures have finite
length scales.
