  The superconducting gap function of Sr$_2$RuO$_4$ was investigated by means
of quasiparticle reflection and transmission at the normal
conductor-superconductor interface of Sr$_2$RuO$_4$-Pt point contacts. We found
two distinguishly different types of $dV/dI$ vs $V$ spectra either with a
double-minimum structure or with a zero-bias conductance anomaly. Both types of
spectra are expected in the limit of high and low transparency, respectively,
of the interface barrier between a normal metal and a spin-triplet
superconductor. Together with the temperature dependence of the spectra this
result strongly supports a spin-triplet superconducting order parameter for
Sr$_2$RuO$_4$.
