Since the discovery of superconductivity in magnesium diboride many works have been focused on investigation of superconductivity in diborides with the structure of AlB$_2$ type.  This structure is a characteristic of some superconductive diborides of transition metals [@Kaczorowski]. 

Our attention has been attracted by rhenium borides with the structure different from that of the simple layered diborides, in particular from MgB$_2$. In the Re-B system following compounds are known Re$_3$B, Re$_7$B$_3$, ReB$_2$ and ReB$_3$ [@binary] with the structures different from the AlB$_2$ type.  Superconductivity at $T_c$=2.8 K was found for a rhenium boride referred to Re$_2$B (with undetermined structure) [@Hulm].  Therefore it is interest to check the superconduting properties of the Re-B compounds and to correlate them with the crystal structure. 

The samples of rhenium diborides were synthesized by heating of rhenium with amorphous boron at temperatures from 950 to 1000$^\circ$C in an inert atmosphere.  An increase in the synthesis temperature causes a decomposition of rhenium diboride onto metallic rhenium and Re$_3$B phase. 

The measurements of the ac-susceptibility and resistance temperature dependence shown, that both compounds (ReB$_2$ and Re$_3$B) are superconductors at temperatures slightly above liquid helium.  The temperature of transition into superconductive state for ReB$_2$ is in the range from 4.5 to 6.3 K depending on the boron concentrations.  Measurements of the sample contents by Auger electron spectra shown boron content from 2 to 1.8. 

The Re$_3$B compound displays the temperature of superconductive transition about 4.7 K. Fig.1 illustrates the temperature dependence of the ac-susceptibility and resistivity for this compound.  Diffraction pattern from the powdered sample corresponds to the known Re$_3$B compound with the orthorhombic cell, space group [*Cmcm*]{}, 16 atoms in the cell.  Measured lattice parameters are a=2.8905, b=9.3039, c=7.2641 Å($\pm$ 0.0003) in agreement with the literature data [@Villars]. 

D. Kaczorowski, J. Klamut, A. J. Zaleski, cond-mat/0104479. 

, ASM International (1996). 

J. K. Hulm, Phys.  Rev. [**98**]{}, 1539 (1955). 

P. Villars and L. D. Calvert, [*Pearson’s Handbook of Crystallographic Data for Intermetallic Phases*]{} (American Society for Metals, Metals Park, Oh, 1985).