  An unavoidable task in quantum information processing is how to obtain data
about the state of an individual system by suitable measurements.
Informationally complete measurements are relevant in quantum state tomography,
quantum cryptography, quantum cloning, and other questions. Symmetric
informationally complete measurements (SIC-POVMs) form an especially important
class of such measurements. We formulate some novel properties and relations
for general SIC-POVMs in a finite-dimensional Hilbert space. For a given
density matrix and any general SIC-POVM, the so-called index of coincidence of
generated probability distribution is exactly calculated. Using this result, we
obtain state-dependent entropic bounds for a single general SIC-POVM. Lower
entropic bounds are derived in terms of the R\'{e}nyi $\alpha$-entropies for
$\alpha\in[2;\infty)$ and the Tsallis $\alpha$-entropies for $\alpha\in(0;2]$.
A lower bound on the min-entropy of a SIC-POVM is separately examined. For a
pair of general SIC-POVMs, entropic uncertainty relations of the Maassen-Uffink
type are considered.
