The temperature and frequency dependences of the real and imaginary parts of the complex impedance of ceramic samples of the clathrates of variable composition Sn24P19.3BrxI8x are investigated in the frequency range from 20 to 106Hz at temperatures from 4.2 to 200K. The conductivity of the samples is measured in the dc regime at temperatures from 4.2 to 300K; it is characterized by the presence of an activation part, with energy increasing monotonically from 18 to 77meV as the bromine concentration increases. The impedance spectra are investigated by a graphoanalytical method. As an approximating equivalent circuit, an RC circuit with a frequency-dependent capacitance is considered. It is shown that the capacitive contribution to the admittance falls off sharply with decreasing temperature below 75K and with increasing frequency above 150kHz. The observed dielectric anomalies are attributed to a substantial contribution to the complex impedance from the grain boundaries.

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