Electronic properties of TiSi2 single crystals at low temperatures

We report measurements of Hall effect, transverse magnetoresistance, and specific heat on high-quality TiSi2 (C54 phase) single crystals at low temperatures. We used crystals with low residual resistivity (typically rho(4.2 K)=0.15 mu Omega cm) and magnetic fields (B) up to 20 T. These facts allowed us to study the electronic properties from the low (omega(c) tau much less than 1) to the high field regime (omega(c) tau>1, omega(c)=eB/m* being the cyclotron frequency and tau the electron relaxation time) as a function of magnetic-field strength and temperature. The low field Hall coefficient R(H) is negative, almost constant R(H)=-(0.5+/-0.1)x10(-10) m(3)/C between 100 and 300 K and it changes sign at similar to 30 K. The angular dependence of magnetoresistance shows either minima or maxima when the magnetic field is parallel to the principal crystallographic axes. These structures are, however, less pronounced than in other silicides, such as PdSi2 and NbSi2, and this suggests only a weak anisotropy of the TiSi2 Fermi surface. The galvanomagnetic properties behave consistently with band-structure calculations of Mattheiss and Hensel [Phys. Rev. B 39, 7754 (1989)] who found that TiSi2 is a compensated metal with only closed orbits for the Fermi electrons. Using a simple two-band model we estimated, from the low field magnetoresistance, carrier density n(e)=n(h)=(0.45-0.52)x10(22) cm(-3) assuming equal concentration of electrons and holes. Low temperatures (1.6<22 K) specific-heat (C-p) measurements fit a linear C-p/T=gamma+beta T-2 dependence, with gamma=3.35+/-0.05 mJ/K-2 mol and beta=0.0201+/-0.0005 mJ/K-4 mel. From these parameters we estimated the Debye temperature Theta(D)=662+/-4 K and the renormalized electronic density of states at the Fermi surface N(epsilon(F))(1+lambda)=2.85 states/eV cell.