Recently, non-volume conserving or non-Joulian magnetostriction has been reported in Fe-Ga alloys [Nature 521, 340 (2015); ibid., 538 416 (2016)] that increase their volume by expanding in magnetic fields. Here we report the complementary set of contracting non-Joulian crystals (Fe-Ge, Fe-Al) that decrease their volume. Results provide the critical compositional degree-of-freedom necessary for designing new alloys (beyond the initially reported Fe-Ga alloys) and establish this new family of functional materials based on non-Joulian magnetostriction.