  We study the low-temperature heat transport of Nd_3Ga_5SiO_{14}, which is a
spin-liquid candidate, to probe the nature of ground state and the effect of
magnetic field on the magnetic properties. The thermal conductivity (\kappa)
shows a purely phononic transport in zero field. The external magnetic field
along the c axis induces a dip-like behavior of \kappa(H), which can be
attributed to a simple paramagnetic scattering on phonons. However, the
magnetic field along the ab plane induces another step-like decrease of \kappa.
This kind of \kappa(H) behavior is discussed to be related to a field-induced
partial order, which yields low-energy magnetic excitations that significantly
scatter phonons. These results point to a paramagnetic ground state that
partial magnetic order can be induced by magnetic field along the ab plane,
which is also signified by the low-T specific heat data.
