  We obtained spectra of the pre-main sequence star AU Microscopii during a
transit of its Neptune-sized planet to investigate its orbit and atmosphere. We
used the high-dispersion near-infrared spectrograph IRD on the Subaru telescope
to detect the Doppler "shadow" from the planet and constrain the projected
stellar obliquity. Modeling of the observed planetary Doppler shadow suggests a
spin-orbit alignment of the system ($\lambda=-4.7_{-6.4}^{+6.8}$ degrees), but
additional observations are needed to confirm this finding. We use both the IRD
data and spectra obtained with NIRSPEC on Keck-II to search for absorption in
the 1083 nm line of metastable triplet He I by the planet's atmosphere and
place an upper limit for the equivalent width of 3.7 m\AA at 99 $\%$
confidence. With this limit and a Parker wind model we constrain the escape
rate from the atmosphere to $<0.15-0.45\, M_{\oplus}$ Gyr$^{-1}$, comparable to
the rates predicted by an XUV energy-limited escape calculation and
hydrodynamic models, but refinement of the planet mass is needed for rigorous
tests.
