diff --git a/dhp-workflows/dhp-aggregation/src/main/java/eu/dnetlib/dhp/actionmanager/bipaffiliations/PrepareAffiliationRelations.java b/dhp-workflows/dhp-aggregation/src/main/java/eu/dnetlib/dhp/actionmanager/bipaffiliations/PrepareAffiliationRelations.java
index 20c649a74..45e712c7e 100644
--- a/dhp-workflows/dhp-aggregation/src/main/java/eu/dnetlib/dhp/actionmanager/bipaffiliations/PrepareAffiliationRelations.java
+++ b/dhp-workflows/dhp-aggregation/src/main/java/eu/dnetlib/dhp/actionmanager/bipaffiliations/PrepareAffiliationRelations.java
@@ -4,6 +4,8 @@ package eu.dnetlib.dhp.actionmanager.bipaffiliations;
 import static eu.dnetlib.dhp.common.SparkSessionSupport.runWithSparkSession;
 
 import java.io.Serializable;
+import java.util.Arrays;
+import java.util.List;
 import java.util.stream.Collectors;
 
 import eu.dnetlib.dhp.actionmanager.Constants;
@@ -18,6 +20,7 @@ import org.apache.hadoop.mapred.SequenceFileOutputFormat;
 import org.apache.spark.SparkConf;
 import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
+import org.apache.spark.api.java.function.FlatMapFunction;
 import org.apache.spark.api.java.function.MapFunction;
 import org.apache.spark.sql.Encoders;
 import org.apache.spark.sql.SparkSession;
@@ -38,7 +41,6 @@ import scala.Tuple2;
  */
 public class PrepareAffiliationRelations implements Serializable {
 
-    private static final String DOI = "doi";
     private static final Logger log = LoggerFactory.getLogger(PrepareAffiliationRelations.class);
     private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
     private static final String ID_PREFIX = "50|doi_________::";
@@ -102,7 +104,7 @@ public class PrepareAffiliationRelations implements Serializable {
 
         // prepare action sets for affiliation relations
         affiliationRelations
-            .map((MapFunction<AffiliationRelationModel, Relation>) affRel -> {
+            .flatMap((FlatMapFunction<AffiliationRelationModel, Relation>) affRel -> {
 
                 // DOI to OpenAIRE id
                 final String paperId = ID_PREFIX + IdentifierFactory.md5(CleaningFunctions.normalizePidValue("doi", affRel.getDoi()));
@@ -125,15 +127,8 @@ public class PrepareAffiliationRelations implements Serializable {
                    qualifier,
                    Double.toString(affRel.getConfidence()));
 
-                return OafMapperUtils.getRelation(
-                    paperId,
-                    affId,
-                    ModelConstants.RESULT_ORGANIZATION,
-                    ModelConstants.AFFILIATION,
-                    ModelConstants.HAS_AUTHOR_INSTITUTION,
-                    null,
-                    dataInfo,
-                    null);
+                // return bi-directional relations
+                return getAffiliationRelationPair(paperId, affId, dataInfo).iterator();
 
             }, Encoders.bean(Relation.class))
             .toJavaRDD()
@@ -144,4 +139,27 @@ public class PrepareAffiliationRelations implements Serializable {
             .saveAsHadoopFile(outputPath, Text.class, Text.class, SequenceFileOutputFormat.class);
 
     }
+
+    private static List<Relation> getAffiliationRelationPair(String paperId, String affId, DataInfo dataInfo) {
+        return Arrays.asList(
+            OafMapperUtils.getRelation(
+                paperId,
+                affId,
+                ModelConstants.RESULT_ORGANIZATION,
+                ModelConstants.AFFILIATION,
+                ModelConstants.HAS_AUTHOR_INSTITUTION,
+                null,
+                dataInfo,
+                null),
+            OafMapperUtils.getRelation(
+                affId,
+                paperId,
+                ModelConstants.RESULT_ORGANIZATION,
+                ModelConstants.AFFILIATION,
+                ModelConstants.IS_AUTHOR_INSTITUTION_OF,
+                null,
+                dataInfo,
+                null)
+        );
+    }
 }