Parboil carrots in a pot of boiling water for 1 minute. Drain and run under cold water to cool completely. Layer carrots vertically in 2 mason jars. Place a garlic clove in each jar. Heat vinegar, water, sugar, salt, and coriander seeds in a sauce pan over medium high heat. Bring to a boil and lower heat. Simmer a few minutes until salt and sugar have dissolved. Pour hot liquid over the carrots. Distribute liquid and spices evenly between two jars. Secure lids tightly and refrigerate. Pickles will be ready to eat in about 24 hours and will keep in the refrigerator for about a month.