  We analyze surface electromagnetic waves with hyperbolic dispersion supported
at the interface between a semi-infinite isotropic medium and an effective
uniaxial material. Apart from known types plasmons with hyperbolic dispersion
curve, sometimes referred to as Dyakonov plasmons [Z. Jacob and E. E.
Narimanov, APL 93, 221109 (2008)], we classify two new types of surface waves
with hyperbolic dispersion. One type of such waves, in contrary to Dyakonov
plasmons, does not require hyperbolic metamaterials to be involved. These
hybrid-polarized plasmon modes with both TE and TM electromagnetic components
are directional. Their propagation direction can be controlled by changing
material parameters.
