  We present spatially-resolved, rest-frame optical spectroscopy of a z~3
Lyman-break galaxy (LBG), Q0347-383 C5, obtained with SINFONI on the VLT. This
galaxy, among the ~10% brightest LBGs, is only the second z~3 LBG observed with
an integral-field spectrograph. It was first described by Pettini et al.
(2001), who obtained WFPC2 F702W imaging and longslit spectroscopy in the
K-band. We find that the emission line morphology is dominated by two
unresolved blobs at a projected distance of ~5 kpc with a velocity offset of
~33 km s^-1. Velocity dispersions suggest that each blob has a mass of ~10^10
M_sun. Unlike Pettini et al. (2001), our spectra are deep enough to detect
H-beta, and we derive star-formation rates of ~20-40 M_sun yr^-1, and use the
H-beta/[OIII] ratio to crudely estimate an oxygen abundance 12+[O/H]=7.9-8.6,
which is in the range typically observed for LBGs. We compare the properties of
Q0347-383 C5 with what is found for other LBGs, including the gravitationally
lensed ``arc+core'' galaxy (Nesvadba et al. 2006), and discuss possible
scenarios for the nature of the source, namely disk rotation, a
starburst-driven wind, disk fragmentation, and merging of two LBGs. We favor
the merging interpretation or bright, extended LBGs like Q0347-383C5, in broad
agreement with predicted merger rates from hierarchical models.
