Spontaneous structural distortion and quasi-one-dimensional quantum confinement in a single-phase compound.

Oxide heterointerfaces often trigger unusual electronic properties that are absent in respective bulks. Here, direct evidence is offered for spontaneously assembled local structural distortions in a single-phase bulk, which confine electrons to within an atomic layer with notable orbital reconstruction and coupling, close the forbidden band, induce a ferromagnetic ordering, and give rise to a strongly anisotropic, spin-polarized quasi-one-dimensional electron gas.