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We present a single epoch of high signal-to-noise ratio spectropolarimetry ofthe Type Ia supernova (SN Ia) 2004S taken nine days after maximum light. Theflux spectrum is normal, but with the additional presence of high-velocity (HV)line features in both Ca II and Fe II. The object shows continuum polarizationat the 0.4% level in the red, a value which appears to be typical of SNe Ia.The continuum data are consistent with a ~10% global asphericity in anaxisymmetric geometry. Unlike previous observations of other SNe Ia with HVfeatures, the HV features in SN 2004S show no strong polarimetric signature,though this may be due to the timing of our observations. Instead, the objectshows line polarization features (P < 0.5%) that are rotated with respect tothe axis of symmetry of the continuum. The line features are visible in Si II,Fe II, and Ca II, and appear to be narrowly confined in velocity space justabove the photosphere. These polarization features are a result ofcompositional inhomogeneities in the ejecta. They may represent newlysynthesized elements whose clumpy spatial distribution within the ejecta isdistinct from that of the globally aspherical ejecta as a whole.Comment: 25 pages, 6 figures, AJ, minor revisions to match accepted journal  versio

DEVIATIONS FROM AXISYMMETRY REVEALED BY LINE POLARIZATION IN THE NORMAL TYPE Ia SUPERNOVA 2004S