  We propose a new formulation of manifestly Lorentz-covariant spinor
wave-packet basis. The conventional definition of the spinor wave packet is
problematic in the sense that it suffers from mixing with other wave packets
under Lorentz transformations. Our formulation evades this difficulty of
mixing. This wave packet forms a complete set that can expand a free spinor
field in a Lorentz covariant manner. In addition, we present a
Lorentz-invariant expression of zero-point energy.
