  The paper describes a study of the magnetic, transport and magnetoresistive
properties of La_{1-x}Ca_{x}MnO_{3} (x\approx 0.33) crystals prepared by the
floating-zone method. We found that these properties testify to rather good
crystal perfection of the sample studied. In particular, a huge
magnetoresistance ([R(0)-R(H)]/R(H) in the field H = 5 T is about 2680 %) is
found near the Curie temperature (216 K). At the same time, some distinct
features of measured properties indicate the influence of extrinsic
inhomogeneities arising due to technological factors in the sample preparation.
Analysis of the data obtained shows that these are rare grain boundaries and
twins. Specific influence of the grain-boundary-like inhomogeneities on the
transport and magnetoresistive properties are considered.
