sherpa: Could not find a package configuration file provided by "k2"

I have successfully installed k2, but when i try to install sherpa, it came out the following errors:

CMake Error at cmake/k2.cmake:19 (find_package):
  By not providing "Findk2.cmake" in CMAKE_MODULE_PATH this project has asked
  CMake to find a package configuration file provided by "k2", but CMake did
  not find one.

  Could not find a package configuration file provided by "k2" with any of
  the following names:

    k2Config.cmake
    k2-config.cmake

  Add the installation prefix of "k2" to CMAKE_PREFIX_PATH or set "k2_DIR" to
  a directory containing one of the above files.  If "k2" provides a separate
  development package or SDK, be sure it has been installed.
Call Stack (most recent call first):
  CMakeLists.txt:44 (include)