NMR Tl-203 and Tl-205 spectra of TlZrF5 have been measured. The large
Tl-205 chemical shift anisotropy (Delta sigma(xx) = 510 +/- 10 ppm; De
lta sigma(yy) = 90 +/- 10 ppm; Delta sigma(zz) = -600 +/- 10 ppm; [sig
ma](R) = -170 +/- 10 ppm) and indirect exchange interaction of Tl-203,
Tl-205 nuclear spins in Tl layers (J = 14.4 kHz; B = 3.5 kHz) reveal t
he involvement of 6s6p sigma hybrid orbitals in the Tl-Tl bonding. The
energy gap between the bonding hybrid 6s6p sigma, and nonbonding 6s(2
) orbitals is Delta E = (36.5 +/- 0.6) x 10(-3) eV.