Rccrived 1-I Ikccmbcr 1982 FPR spectra attriburable to TI, "+ ion Pairs have been detected in single crystals of Ti60,, at temperatures below 147 I-C;. The spin count associated \vith-Tir varies with temperature. This and other changes in the spectrum accompanying ~hc phase transition at 119 E are discussed in the light of structural data. f _ Introduction The "hiagntili phases" of titauiurn and vanadhn asides have stimulated considerable interest as many of them exhibit sharp discontinuities in certain physical properties when heated or cooled_ In particular, Ti,O, , shows a sudden and reversible increase in electrical conductivity when cooled through the lower of its two transition temperatures [ 11. Electron paramagnetic resonance (EPR) experiments on this compound have previously been reported r2.31) but they were carried out ou polycrystalline samples, and ignorance oi the recently discovered transition at 119 K made the discussiou somewhat inadequate_ We report here rhe results ofan EPRstudy ofsingle cryst:rls of Ti,O, , . The samples were studied in three 1cuqwra[ure rauges -below 119 K, between 119 and 117 K. and above 147 K. The EPR spectra are discussed iu ihe light ofcurrent kuowledge of the struc-ILJK. and are attributed to a single unpaired electron shared by a pair of titanium ions. i.e. a Tip cluster.