  We report the discovery of a boundary-induced body-centered tetragonal (bct)
iron phase in thin films deposited on MgAl$_{2}$O$_{4}$ ($001$) substrates. We
present evidence for this phase using detailed x-ray analysis and ab-initio
density functional theory calculations. A lower magnetic moment and a rotation
of the easy magnetisation direction are observed, as compared to body-centered
cubic (bcc) iron. Our findings expand the range of known crystal and magnetic
phases of iron, providing valuable insights for the development of
heterostructure devices using ultra-thin iron layers.
