UCoAl exhibits attributes of an itinerant 5f-electron metamagnet. It is paramagnetic down to lowest temperatures but the c-axis susceptibility shows a maximum around Tmax ≈ 20 K. When a field larger than Bc ≈ 0.6 T is applied along the c-axis of hexagonal structure a ferromagnetic ordering of U moments is induced at low temperatures. The critical parameters Tmax and Bc are sensitive to alloying and hydrostatic pressure. In the latter case values of both, Tmax and Bc, are increasing with increasing pressure, i.e. metamagnetism is suppressed towards a conventional paramagnetism. We report on results of an experiment with a c-axis uniaxial pressure, which has an opposite influence on Tmax and Bc leading to ferromagnetism in zero field. A scenario of the physics of UCoAl is presented accounting for effects of hydrostatic- and uniaxial-pressure on the lattice and consequences in the 5f-electron delocalization and anisotropy of hybridization-mediated exchange interactions.
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