  We propose a ferromagnetic Heusler alloy that can switch between a metal and
a half-metal. Thiseffect can provide tunable spintronics properties. Using the
density functional theory (DFT) withreliable implementations of the electron
correlation effects, we find Mn2ScSi total energy curvesconsisting of distinct
branches with a very small energy difference. The phase at low lattice
crystalvolume is a low magnetic half-metallic state while the phase at high
lattice crystal volume is a highmagnetic metallic state. We suggest that the
transition between half-metallic and metallic statescan be triggered by a
triaxial contraction/expansion of the crystal lattice or by an external
magneticfield if we assume that the lattice is cubic and remains cubic under
expansion/contraction. However,the phase at high volume can also undergo an
austenite-martensite phase transition because of thepresence of Jahn-Teller
active3delectrons on the Mn atoms.
