Electronic phase transition and an anomalous ordered phase in Ba2Ti13O22 with 3d1 ions on a triangle-based lattice.

We found that Ba(2)Ti(13)O(22) with Ti(3+) (3d(1)) ions on a triangle-based lattice exhibits a phase transition at T(c)~200 K, below which the increase of electrical resistivity and decrease of magnetic susceptibility were observed. Transmission electron microscopy and optical reflectivity measurements indicate that the low-temperature phase of the present compound shares characteristics in common with a charge-density-wave state with remnant carriers, although a commensurate wave vector of the modulation and a linear temperature dependence of the magnetic susceptibility below T(c) suggest an exotic ordered state.