  We investigated the anomalous peak resistivity below the onset $T_c$ in
underdoped YBCO, reminiscent of that observed in 1D wires of conventional
superconductors. We performed measurements of the angular dependence of
resistivity $\rho(\theta)$ in a magnetic field and the temperature dependence
of resistivity $\rho(T)$, which exhibit a peak for $\textbf{B} \parallel$
ab-planes. This peak in $\rho(T)$ disappears for $\textbf{B} \parallel$ c-axis.
The width of the corresponding maximum in $\rho(\theta)$ at $\theta=0^o$
($\textbf{B} \parallel$ ab-planes) decreases with increasing c-axis component
of the field ($B \sin \theta$). The maximum in $\rho(\theta)$ and $\rho(T)$
decreases with an increasing applied transport current. We analyzed the data
using three different models of resistivity based on 2D resistor array, flux
motion, and thermally activated phase-slips. Numerical calculations suggest
that in a filamentary underdoped system, the phase-slip events could produce
the anomalous resistivity close to $T_c$.
