  The metallic conductivity of dilute two-dimensional holes in a GaAs HIGFET
(Heterojunction Insulated-Gate Field-Effect Transistor) with extremely high
mobility and large $r_{s}$ is found to have a linear dependence on temperature,
consistent with the theory of interaction corrections in the ballistic regime.
Phonon scattering contributions are negligible in the temperature range of our
interest, allowing comparison between our measured data and theory without any
phonon subtraction. The magnitude of the Fermi liquid interaction parameter
$F_{0}^{\sigma}$ determined from the experiment, however, decreases with
increasing $r_{s}$ for $r_{s}\agt22$, a behavior unexpected from existing
theoretical calculations valid for small $r_{s}$.
