  By the application of a small oscillating magnetic field parallel to the main
magnetic field and perpendicular to the transport current, we were able to
unveil the peak effect in the resistivity data of Nb$_3$Sn near the upper
critical field $H_{c2}$. We investigated the dependence of this effect on the
frequency and the amplitude of the oscillating magnetic field and show that the
used technique can be more sensitive to detect the peak effect in a certain
range of temperatures and magnetic fields than conventional magnetization
measurements.
