  Transport behavior characterized by a low-temperature electrical resistivity
that displays a power-law behavior $\rho(T\to 0) \propto T^s$ with an exponent
$s<2$, is commonly observed in magnetic materials in both the magnetic and
nonmagnetic phases. We give a pedagogical overview of this phenomenon that
summarizes both the experimental situation and the state of its theoretical
understanding. We also put it in context by drawing parallels with unusual
power-law transport behavior in other systems.
