Milky Way Mid-Infrared Spitzer Spectroscopic Extinction Curves: Continuum and Silicate Features

We measured the mid-infrared (MIR) extinction using Spitzer photometry and spectroscopy (3.6--37 micron) for a sample of Milky Way sightlines (mostly) having ultraviolet curves. used pair method to determine MIR that we then fit with power law continuum modified Drude profiles silicate features. derived 16 curves range A(V) (1.8-5.5) R(V) values (2.4-4.3). Our includes two dense have 3 micron ice feature detections weak 2175 A bumps. The average A(lambda)/A(V) diffuse sightline curve calculate is lower than most previous literature measurements. This agrees better dust grain models, though it somewhat higher. 10 does not correlate bump, first time providing direct observational confirmation these features arise from different populations. strength varies by $\sim$2.5 correlated or R(V). It well profile strong correlations seen between central wavelength, width, asymmetry. do detect other limits in units 0.0026 (5--10 micron), 0.004 (10--20 0.008 (20-40 micron). find standard prescription estimating C times E(K_s-V)/E(B-V) has = -1.14 scatter $\sim$7%. Using IRAC 5.6 band instead K_s gives -1.03 least $\sim$3\%.