  We consider the Schr\"odinger operator with a periodic potential $p$ on the
real line. We assume that $p$ belongs to the Sobolev space $\mH_m$ on the
circle for some $m\ge -1$, and we determine the asymptotics of the
quasimomentum and the Titchmarsh-Weyl functions, the Bloch functions at high
energy.
