We investigated the half-metallicity and magnetism at the (001) and (110) surfaces of YC in zinc-blende
structure by using the all-electron full-potential linearized augmented plane wave method within the
generalized gradient approximation. From the calculated local density of states, we found that neither (001) nor (110) surface preserves the half-metallicity. While the magnetic moment of Y atom in the YC bulk is 0.116 μB, it is 0.057 μB at the topmost layer of Y-terminated (001) surface. On the contrary, C-terminated (001) YC surface exhibits stronger magnetism than the bulk structure; the calculated magnetic moment on topmost C atom is 1.084 μB, while that of C atom in the bulk structure is 0.423 μB. The magnetic properties of the non-polar (110) YC surface are slightly enhanced as compared with the bulk structure.