Chiral Crystal Structure and Split Fermi Surface Properties in TaSi2

We carried out a de Haas-van Alphen (dHvA) experiment in TaSi2 with the hexagonal chiral structure, together with an energy band calculation. The Fermi surface is found to be split into two different Fermi surfaces, reflecting the non-centrosymmetric crystal structure. The magnitude of the antisymmetric spin-orbit interaction or the splitting energy between the two Fermi surfaces is determined to be 493K for dHvA branch alpha (alpha'), 564K for branch beta (beta'), and 617K for branch gamma (gamma'), where these dHvA branches correspond to the main Fermi surfaces. The present splitting values are compared with 19, 39, and 110 K, respectively, observed in a similar compound, VSi2. The splitting energy is found to be larger in Ta-5d conduction electrons than in V-3d conduction electrons. Furthermore, we found a magnetic breakthrough effect for branches gamma (gamma') and alpha (alpha'), of which the circulating orbits are separate but are nearly degenerate in three and two regions, respectively.