The 2D features of the electronic structure of the layered
diboride dicarbide YB2C2 superconductor

Sergii Khmelevskyi

Center for Computational Material Science, Technical University of Vienna, Getreidemarkt 9/134, A-1060 Vienna, Austria

The electronic structure of the layered diboride dicarbide superconductor YB2C2 is calculated using the full potential LAPW method within the framework of ab initio density functional theory. Our results confirm that the crystal structure with P4/mbm symmetry is more stable than the originally claimed P42c structure, which is in accordance with recent interpretations of the diffraction patterns of other related compounds of LaB2C2-type. It is found that the metallic conductivity in the stable P4/mbm structure is due to Y d-bands partially hybridized with pz-states from the B-C planes. Thus the structure of the conduction bands differs from those found in MgB2. However, a large portion of the Fermi surface of YB2C2 exhibits distinctive two-dimensional features, which can make this compound interesting for experimental studies on superconductivity connected to effects of strong electronic structure anisotropy. The interesting finding is also that unstable P42c structure have in contrast open conduction sigma-band similar to those in MgB2.