  We detected an emission line feature at 4 keV in the X-ray spectrum of a sky
region including the distant radio galaxy 3C220.1(z=0.62) obtained with ASCA.
The line energy is 6.1 - 7.0 keV (90% confidence) in the rest frame of 3C220.1.
Within the present statistics, the observed spectra are consistent with two
different models; a non-thermal model consisting of a power-law continuum plus
a 6.4 keV iron emission line, and a Raymond-Smith thin-thermal emission model
of kT ~6 keV with a metal abundance of ~0.5 solar. However, the large (~500 eV)
equivalent width of the line indicates that a significant fraction of the X-ray
emission is likel y to arise from the hot intracluster gas which associates the
galaxy cluster including 3C220.1. The spectral parameters of the thermal
emission is consistent with the luminosity-temperature relation of nearby
clusters and the mass estimates from the giant luminous arc.
