  We have studied the charge-density-wave (CDW) state for the superconducting
Lu$_5$Ir$_4$Si$_{10}$ and the antiferromagnetic Er$_5$Ir$_4$Si$_{10}$ as
variables of temperature, magnetic field, and hydrostatic pressure. For
Lu$_5$Ir$_4$Si$_{10}$, the application of pressure strongly suppresses the CDW
phase but weakly enhances the superconducting phase. For Er$_5$Ir$_4$Si$_{10}$,
the incommensurate CDW state is pressure independent and the commensurate CDW
state strongly depends on the pressure, whereas the antiferromagnetic ordering
is slightly depressed by applying pressure. In addition, Er$_5$Ir$_4$Si$_{10}$
shows negative magnetoresistance at low temperatures, compared with the
positive magnetoresistance of Lu$_5$Ir$_4$Si$_{10}$.
