  The isovalent-substituted iron pnictide compound
SrFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ exhibits multiple evidence for nodal
superconductivity via various experimental probes, such as the penetration
depth, nuclear magnetic resonance and specific heat measurements. The direct
identification of the nodal superconducting (SC) gap structure is challenging,
partly because the presence of nodes is not protected by symmetry but instead
caused by an accidental sign change of the order parameter, and also because of
the three-dimensionality of the electronic structure. We have studied the SC
gaps of SrFe$_{2}$(As$_{0.65}$P$_{0.35}$)$_{2}$ in three-dimensional momentum
space by synchrotron and laser-based angle-resolved photoemission spectroscopy.
The three hole Fermi surfaces (FSs) at the zone center have SC gaps with
different magnitudes, whereas the SC gaps of the electron FSs at the zone
corner are almost isotropic and $k_{z}$-independent. We propose that the SC gap
of the outer hole FS changes sign around the Z-X [($0, 0, 2\pi$)-($\pi,\pi,
2\pi$)] direction.
