Three-Dimensional Band Structure of Sr$_4$Ru$_3$O$_{10}$*

The electronic structure and Fermi Surface (FS) of the triple-layer ruthenate Sr$_4$Ru$_3$O$_{10}$ is probed with angle resolved photoemission. Angle-dependent FS maps show distinctly different sized FS orbits as compared to the measured single- and double-layer ruthenate FS topologies. In addition, photon-dependent FS maps reveal a distinct k$_{\perp}$ variation with a periodicity corresponding to the inter-layer spacing of the triple-layer stack, indicating a three-dimensionality of the band structure. Comparison of the FS topology is made to available band structure calculations.