Topological Change of the Fermi Surface in Ternary Iron Pnictides with Reduced c/a Ratio: A de Haas-van Alphen Study of CaFe2P2

We report a de Haas-van Alphen effect study of the Fermi surface of CaFe2P2 using low-temperature torque magnetometry up to 45 T. This system is a close structural analog of the collapsed tetragonal nonmagnetic phase of CaFe2As2. We find the Fermi surface of CaFe2P2 to differ from other related ternary phosphides in that its topology is highly dispersive in the c axis, being three dimensional in character and with identical mass enhancement on both electron and hole pockets (similar to 1.5). This suggests that when the bonding between pnictogen layers becomes important nesting conditions are not fulfilled.