  The concept of well-rounded lattices has recently found important
applications in the setting of a fading single-input single-output (SISO)
wiretap channel. It has been shown that, under this setup, the property of
being well-rounded is critical for minimizing the eavesdropper's probability of
correct decoding in lower SNR regimes. The superior performance of coset codes
constructed from well-rounded lattices has been illustrated in several
simulations.
  In the present article, this work is extended to fading multiple-input
multiple-output (MIMO) wiretap channels, and similar design criteria as in the
SISO case are derived. Further, explicit coset codes for Rayleigh fading MIMO
wiretap channels are designed. In particular, it is shown through extensive
simulations that sublattices of the well-known Alamouti code and Golden code
which meet our design criteria perform better than scalar multiples of the code
lattice for the same parameters.
