  Polarization-adjusted convolutional (PAC) codes were recently proposed and
arouse the interest of the channel coding community because they were shown to
approach theoretical bounds for the (128,64) code size. In this letter, we
propose systematic PAC codes. Thanks to the systematic property, improvement in
the bit-error rate of up to 0.2 dB is observed, while preserving the
frame-error rate performance. Moreover, a genetic-algorithm based construction
method targeted to approach the theoretical bound is provided. It is then shown
that using the proposed construction method systematic and non-systematic PAC
codes can approach the theoretical bound even for higher code sizes such as
(256,128).
