The multifractal properties of electronic eigenstates at the metal-insulator transition of a two-dimensional disordered tight-binding model with spin-orbit interaction are investigated numerically. The correlation dimensions of the spectral measure D 2 and of the fractal eigenstate D 2 are calculated and shown to be related by D 2 = 2 D 2 . The exponent η = 0.35 ± 0.05 describing the energy correlations of the critical eigenstates is found to satisfy the relation η = 2 − D 2 .PACS numbers: 71.30.+h, 64.60.Ak, 72.15.Rn Typeset using REVT E X 1 Electronic states in disordered systems are known to be either localized or extended. At T = 0 the so called mobility edge separates insulating (localized) from current carrying (extended) states. Recently, the electronic properties directly at the critical point have received increasing attention [1][2][3][4][5][6]. Two-dimensional (2d) systems are very well suited for numerical investigations of the electronic eigenstates at a critical point. The only systems, however, that exhibit a complete Anderson transition in 2d are models with symplectic symmetry. This is in contrast to the orthogonal and the unitary case where all states are localized (weak localization) and the quantum Hall (QHE) systems where only localized states with a diverging localization length at some singular energies can be observed.In a recent paper, Chalker and coworkers [7] reported on numerical investigations of eigenstate fluctuations and correlations near the mobility edge of a two-dimensional tight-binding model with spin-orbit coupling. It was found that the probability amplitude distribution exhibits multifractal behavior which can be characterized by a set of generalized dimensions D q . The fractal spatial structure of the wavefunctions also shows up in the eigenfunction correlations between states close in energy. A similar behavior was found also in the quantum Hall model [1,[8][9][10], i.e. a two-dimensional disordered system of non-interacting electrons where a strong magnetic field causes the localization length to diverge at the centres of the Landau bands with a universal exponent [11]. For these critical states, characteristic quantities like the generalized correlation dimension of the wavefunction D 2 = 1.62 [8,9], the corresponding generalized dimension of the spectral measure D 2 = 0.81 [3], the exponent η = 0.38 [1,3] governing the energy eigenfunction correlations, and α 0 = 2.3 [9,10] which for −1 < ∼ q < ∼ 1 determines the so called f (α)-distribution are known, partly with sufficient precision. This is, however, not the case for the spin-orbit system mentioned above, mainly because of the small system sizes considered so far (M ≤ 18 a) [7]. The authors of Ref. [7] used a model proposed by Evangelou and Ziman [12] which represents a two-dimensional disordered electronic system with spin-orbit interaction.In this letter, a different lattice model with symplectic symmetry is investigated for system sizes up to 150 a × 150 a, where a is the lattice constant. It is fou...