  We report experimental measurements showing how one can combine quantum
interference and thermal Doppler shifts at room temperature to detect weak
magnetic fields. We pump ${}^{87}$Rb atoms to a highly-excited, Rydberg level
using a probe and a coupling laser, leading to narrow transmission peaks of the
probe due to destructive interference of transition amplitudes, known as
Electromagnetically Induced Transparency (EIT). While it is customary in such
setups to use counterpropagating lasers to minimize the effect of Doppler
shifts, here we show, on the contrary, that one can harness Doppler shifts in a
copropagating arrangement to produce an enhanced response to a magnetic field.
In particular, we demonstrate an order-of-magnitude bigger splitting in the
transmission spectrum as compared to the counterpropagating case. We explain
and generalize our findings with theoretical modelling and simulations based on
a Lindblad master equation. Our results pave the way to using quantum effects
for magnetometry in readily deployable room-temperature platforms.
