Electronic structure of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ThPd</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Al</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math> : Impact of the U <mml:math xmlns:mml="http://www.w3.org/1998/Math

The electronic structure of ThPd$_2$Al$_3$, which is isostructural to the heavy fermion superconductor UPd$_2$Al$_3$, was investigated by photoelectron spectroscopy. The band structure and Fermi surfaces of ThPd$_2$Al$_3$ were obtained by angle-resolved photoelectron spectroscopy (ARPES), and the results were well-explained by the band-structure calculation based on the local density approximation. The comparison between the ARPES spectra and the band-structure calculation suggests that the Fermi surface of ThPd$_2$Al$_3$ mainly consists of the Al $3p$ and Th $6d$ states with a minor contribution from the Pd $4d$ states. The comparison of the band structures between ThPd$_2$Al$_3$ and UPd$_2$Al$_3$ argues that the U $5f$ states form Fermi surfaces in UPd$_2$Al$_3$ through hybridization with the Al $3p$ state in the Al layer, suggesting that the Fermi surface of UPd$_2$Al$_3$ has a strong three-dimensional nature.