Far Ultraviolet Spectroscopic Explorer spectroscopy of high-velocity cloudcomplex C

We present Far Ultraviolet Spectscopic Explorer (FUSE) observations of the sight line toward the Seyfert 1 galaxy Markarian 876, which passes through high-velocity cloud (HVC) complex C. This sight line demonstrates the abili ty of FUSE to measure ionic absorption lines in Galactic HVCs. High-velocit y absorption is clearly seen in both members of the O VI doublet. This is t he first detection of O VI in a neutral hydrogen HVC, One component of HVC complex C is resolved in multiple Fe II lines from which we derive N(Fe II) /N(H I) = 0.48 (Fe/H).. This value of N(Fe II)IN(H I) implies that the meta llicity of complex C along this sight line may be higher than that along th e Mrk 290 sight line (0.1 solar) found by Wakker et al. On the other hand, if the metallicity of complex C is also 0.1 solar along this line of sight, the observed value of N(Fe II)IN(H I) suggests: there may be a significant amount of He along the line of sight. In any case, little, if any, iron ca n be depleted into dust grains if the intrinsic metallicity of complex C is subsolar. Absorption from complex C is also seen in C II, N I, and N II, a nd upper limits based on nondetections can be determined for Ar r, P II, an d Fe In. Although molecular hydrogen in the Milky Way is obvious in the FUS E data, no H, absorption is seen in the HVC to a limit N(H-2)< 2.0 x 10(14) cm(-2). Future FUSE observations of extragalactic objects behind Galactic HVCs will allow us to better constrain models of HVC origins.