  We performed inelastic neutron scattering on powder sample of the P-doped
iron-based superconductor BaFe2(As0.65P0.35)2 with Tc = 30K, whose
superconducting (SC) order parameter is expected to have line nodes. We have
observed spin resonance at Q $\sim$ 1.2{\AA}^{-1} and E=12 meV in the SC state.
The resonance enhancement, which can be a measure of the area of sign reversal
between the hole and electron Fermi surfaces (FSs), is comparable to those of
other iron-based superconductors without line nodes. This fact indicates that
the sign reversal between the FSs is still dominant in this system, and the
line nodes should create only limited area of sign-reversal on a single FS.
Hence the system can hold relatively high-Tc. Comparison with theoretical
calculation indicates horizontal line nodes may be a candidate to reproduce the
observation.
