  Oxide heterointerfaces constitute a rich platform for realizing novel
functionalities in condensed matter. A key aspect is the strong link between
structural and electronic properties, which can be modified by interfacing
materials with distinct lattice symmetries. Here we determine the effect of the
cubic-tetragonal distortion of $\text{SrTiO}_3$ on the electronic properties of
thin films of $\text{SrIrO}_3$, a topological crystalline metal hosting a
delicate interplay between spin-orbit coupling and electronic correlations. We
demonstrate that below the transition temperature at 105 K, $\text{SrIrO}_3$
orthorhombic domains couple directly to tetragonal domains in $\text{SrTiO}_3$.
This forces the in-phase rotational axis to lie in-plane and creates a binary
domain structure in the $\text{SrIrO}_3$ film. The close proximity to the
metal-insulator transition in ultrathin $\text{SrIrO}_3$ causes the individual
domains to have strongly anisotropic transport properties, driven by a
reduction of bandwidth along the in-phase axis. The strong structure-property
relationships in perovskites make these compounds particularly suitable for
static and dynamic coupling at interfaces, providing a promising route towards
realizing novel functionalities in oxide heterostructures.

Materials Science;Strongly Correlated Electrons