We analyze the dependence of the transmission profiles of an atom in a tripod configuration on the polarizations of the coupling and the probe beams and use room-temperature metastable helium (4He*) as a model system. We show that, by rotating the orthogonally polarized coupling-probe beams with respect to an applied small magnetic field, one can manipulate the detuned peaks due to electromagnetically induced transparency and the central peak arising because of ground-state coherent population oscillations observed earlier separately. Our experimental results match well with our numerical simulation using the Floquet method. © 2013 American Physical Society.