  We report the detection of spiral substructure in both the gas velocity and
temperature structure of the disk around TW~Hya, suggestive of planet-disk
interactions with an unseen planet. Perturbations from Keplerian rotation
tracing out a spiral pattern are observed in the SE of the disk, while
significant azimuthal perturbations in the gas temperature are seen in the
outer disk, outside 90~au, extending the full azimuth of the disk. The
deviation in velocity is either $\Delta v_{\phi} \, / \, v_{\rm kep} \sim 0.1$
or $\Delta v_{z} \, / \, v_{\rm kep} \sim 0.01$ depending on whether the
perturbation is in the rotational or vertical direction, while radial
perturbations can be ruled out. Deviations in the gas temperature are $\pm 4$ K
about the azimuthally averaged profile, equivalent to deviations of $\Delta
T_{\rm gas} \, / \, T_{\rm gas} \sim 0.05$. Assuming all three structures can
be described by an Archimedean spiral, measurements of the pitch angles of both
velocity and temperature spirals show a radially decreasing trend for all
three, ranging from 9$^{\circ}$ at 70 au, dropping to 3$^{\circ}$ at 200 au.
Such low pitch-angled spirals are not readily explained through the wake of an
embedded planet in the location of previously reported at 94 au, but rather
require a launching mechanism which results in much more tightly wound spirals.
Molecular emission tracing distinct heights in the disk is required to
accurately distinguish between spiral launching mechanisms.
