  When a three-level atomic wavepacket is obliquely incident on a "edium slab"
consisting of two far-detuned laser beams, there exists lateral shift between
reflection and incident points at the surface of a "medium slab", analogous to
optical Goos-Hanchen effect. We evaluate lateral shifts for reflected and
transmitted waves via expansion of reflection and transmission coefficients, in
contrast to the stationary phase method. Results show that lateral shifts can
be either positive or negative dependent on the incident angle and the atomic
internal state. Interestingly, a giant lateral shift of transmitted wave with
high transmission probability is observed, which is helpful to observe such
lateral shifts experimentally. Different from the two-level atomic wave case,
we find that quantum interference between different atomic states plays crucial
role on the transmission intensity and corresponding lateral shifts.
