Topological metal behavior in GeBi2Te4 single crystals
  The metallic character of the GeBi2Te4 single crystals is probed using a combination of structural and physical properties measurements, together with density functional theory (DFT) calculations. The structural study shows distorted Ge coordination polyhedra, mainly of the Ge octahedra. This has a major impact on the band structure, resulting in bulk metallic behavior of GeBi2Te4, as indicated by DFT calculations. Such calculations place GeBi2Te4 in a class of a few known non-trivial topological metals, and explains why an observed Dirac point lies below the Fermi energy at about -0.12eV. A topological picture of GeBi2Te4 is confirmed by the observation of surface state modulations by scanning tunneling microscopy (STM). 
A. Marcinkova, J. K. Wang, C. Slavonic, Andriy H. Nevidomskyy, K. F.   Kelly, Y. Filinchuk, and E. Morosan
cond-mat.mtrl-sci