  Conducting and magnetic properties of a material often change in some
confined geometries. However, a situation where a non-magnetic semiconductor
becomes both metallic and magnetic at the surface is quite rare, and to the
best of our knowledge has never been observed in experiment. In this work, we
employ first-principles electronic structure theory to predict that such a
peculiar magnetic state emerges in a family of quaternary Heusler compounds. We
investigate magnetic and electronic properties of CoCrTiP, FeMnTiP and CoMnVAl.
For the latter material, we also analyse the magnetic exchange interactions and
use them for parametrizing an effective spin Hamiltonian. According to our
results, magnetism in this material should persist at temperatures at least as
high as 155 K.
