  We investigated the magnetic and structural properties of the quasi-one
dimensional 3$d^1$-quantum chain system TiPO$_4$ ($J \sim$ 965 K) by magnetic
susceptibility, heat capacity, ESR, x-ray diffraction, NMR measurements, and by
density functional calculations. TiPO$_4$ undergoes two magnetostructural phase
transitions, one at 111 K and the other at 74 K. Below 74 K, NMR detects two
different $^{31}$P signals and the magnetic susceptibility vanishes, while DFT
calculations evidence a bond alternation of the Ti...Ti distances within each
chain. Thus, the 74 K phase transition is a spin-Peierls transition which
evolves from an incommensurate phase existing between 111 K and 74 K.
