  We report the detection of complex Fe K line emission from a Chandra High
Energy Transmission Grating Spectrometer observation of the Seyfert 1 galaxy IC
4329A. The line emission is double-peaked, one peak centered at ~6.3 keV, and
the other at ~6.9 keV in the source rest frame. When modeled by Gaussians, the
lower energy peak is resolved by the HEG at >99% confidence, whilst the higher
energy peak is resolved at only <90% confidence. The best-fitting widths are
\~21,000km/s and ~4000km/s FWHM for the ~6.3 keV and ~6.9 keV peaks
respectively. If the peaks correspond to two distinct emission lines, then the
peak energies are redshifted with respect to the expected line energies of Fe I
Ka and Fe XXVI Lya by at least 650 km/s and 950 km/s respectively.
Alternatively, the Fe K line profile may be due to a single line from a
relativistic accretion disk. In that case the inclination angle of the disk is
required to be 24^{+9}_{-1} degrees, the outer radius constrained to several
tens of gravitational radii, and the radial line emissivity flatter than
r^{-0.7}. Another possibility is that both peaks are due to distinct lines but
each one relativistically broadened by a disk. In that case the lower energy
peak could correspond to emission from Fe in a low ionization state, and the
high-energy peak to Fe XXVI Lya emission. Then, the inclination angle is even
less, restricted to a few degrees. However, the radial emissivity law is
allowed to be steeper (~r^{-2.5}) and the outer radius does not have to be
fine-tuned. Yet another scenario is that the lower energy peak originates in a
disk but the higher energy peak originates in more distant matter.
